General Maintenance & Repairs - Sputtering Under Load

This is for my 98, my daily driver. I was driving in this morning to work and I noticed some hesitation in 6th gear at 65 MPH. Wasn't a big deal I thought. Then, I noticed it at lower gear, and now while accelerating in every gear. It's like a full auto AK-47, for example, in terms of rate (not loudness). It does not happen at idle while revving.

My SES light has been on for months now. It's telling me the driver side cat is bad. On my drive to/from the Hamptons I hit 2389048923480234 bumps, pot holes, etc., mainly on the Belt Parkway & Staten Island Expressway. Is it possible it rattled my cat apart and is now clogged up?

I don't think it's bad gas, but who knows. I've always run Sunoco 93 octane gas. Over the weekend I was in the Hamptons and had to fill with Hess gas. I ran through that tank from Sunday to yesterday, and filled up with Sunoco.

Also thinking possibly plugs? I have 107,XXX miles and do not think that the prior owner changed the plugs or wires.

Any recommendations are appreciated. Thanks.

EDIT: Check Post #13 for an update.

Yes it's time for plugs and wires. What exactly is the code your getting, that makes you think the cat is bad?

Thanks. This is why I think it's the cat: http://ls1tech.com/forums/generation-iii-external-engine/1449624-p0420-best-mpg-yet.html

It does sound like a bad/broken cat, but...

Before addressing that, I'd still do a MAF cleaning first. It's dirt cheap, easy to do, and your K&N makes you more likely to fall victim to a contaminated MAF. If that MAF is reading incorrectly, it can cause your air/fuel to be off and throw off the O2's. Its happened to me in the past, but I got a different SES code. (The code you are getting more closely points to a Cat issue.)

Thanks. Should I clean my MAF or swap it over from my '01? Not sure what years are the same? I may just swap over the OR-Y from the '01 to the '98, then get a new cat for the '01.

I had a K&N soil my MAF and a cleaning with MAF cleaner (specific for the purpose) took care of it and several years, I'm still going strong.

Hmm. Well, I got the CRC MAF cleaner. Cleaned it during my lunch break. Still sputtering - mainly under WOT, but it's still there at other points on and off as well...... I'm going to hook up my scan tool and see if it's throwing any other codes.

Update: I swapped the de-screened MAF (Which was run with an OE paper filter with SLP intake) from my '01 into the '98. I did find a hose that was open (Drive side front wheel well area). It is now blocked off. Didn't really do much of anything. Still sputters basically the same.

So now I'm on to thinking it's the o2 sensor(s) or cat(s)?

BTW - You are incredibly brave to drive from PA/NJ, brave Long Island, and drive to the Hamptons. I did that drive once... Never again. The geography along that route is unique in the world. Its probably the hardest place to get around while being one of the most densely populated...

Have you done a visual inspection of the Cat? If something hit it, you might be able to tell. I'd start by seeing if I could take it off and look at the substrate inside to look for breaks. Do you hear any rattling? (That would be a tell-tale of a broken Cat.)

OK so at 107,000 miles when are you going to change those old plugs? I replaced my cats at about 250,000 miles not exactly sure without going thru my paperwork but I know it was ton of miles before I did.

and what a drive that is, I,m glad I do not have to contend with that any more,especially
the part of being robbed at every bridge crossing, lol.

BTW - You are incredibly brave to drive from PA/NJ, brave Long Island, and drive to the Hamptons. I did that drive once... Never again. The geography along that route is unique in the world. Its probably the hardest place to get around while being one of the most densely populated...

Have you done a visual inspection of the Cat? If something hit it, you might be able to tell. I'd start by seeing if I could take it off and look at the substrate inside to look for breaks. Do you hear any rattling? (That would be a tell-tale of a broken Cat.)

Both cats look okay. No rattling that I have heard for, but need to look a bit more and do some minor thumping of the cat to see what I hear. That drive SUCKED. We left here outside of Philly around 8pm, and got to Sag Harbor around 12:15am. Not too bad IMO. I hit every DAMN bump, pothole, construction hole, etc., on the drive out that. That said, I'd rather be with my car in the Hamptons than take a bus or train. I dunno, I love my f-bodies!




OK so at 107,000 miles when are you going to change those old plugs? I replaced my cats at about 250,000 miles not exactly sure without going thru my paperwork but I know it was ton of miles before I did.

and what a drive that is, I,m glad I do not have to contend with that any more,especially
the part of being robbed at every bridge crossing, lol.


109,000 now ;) I'll look at replacing the plugs shortly. Anyone know the GM recommended mileage to replace LS1 plugs? It had been getting worse and worse as of late. I disconnected my driver side, downstream o2 sensor. I just took it out for a cruise and it drives 98% better than before. Some very minor sputtering coming off of idle. A bit more towards the top of the RPM range as well. Still no time to do any work on it as of yet.

I'd rather be with my car in the Hamptons than take a bus or train. I dunno, I love my f-bodies!

I just keep on driving up 95, until I get to Maine. :) (I can buy an entire lobster up there for what a large order of french fries costs in NY.)


Here's some interesting reading on plugs - http://ls1tech.com/forums/general-maintenance-repairs/1582023-anyone-ever-leave-their-factory-platinum-plugs-100k-miles-i-did.html

Nom nom!! Don't get me started on my love for lobster. My g/f, who is a chef btw, has never had a lobster! She went to UVM for 3 years too, and has been to Maine. That needs to change! Oh, and we're both divers too... so wtf? haha.

I'll check the plugs link, thanks!

Here's an update: I unplugged the driver side, downstream o2. The car runs about 95% better than it does with the o2 plugged in. So this means it's most likely a cat, or one of those o2 sensors on the driver side, correct?

Here's an update: I unplugged the driver side, downstream o2. The car runs about 95% better than it does with the o2 plugged in. So this means it's most likely a cat, or one of those o2 sensors on the driver side, correct?

I don't think I've seen any good definitive information on this. Theoretically... the downstream sensor should just tell you when you have a good/bad cat and should have nothing to do with driveability. But, I have seen GM statements that the readings are put into consideration for the PCM calculations. I don't think I've seen any info on to what degree this plays a part.

I don't think I've seen any good definitive information on this. Theoretically... the downstream sensor should just tell you when you have a good/bad cat and should have nothing to do with driveability. But, I have seen GM statements that the readings are put into consideration for the PCM calculations. I don't think I've seen any info on to what degree this plays a part.

Hmm, beautiful. I'll talk to my tech buddy when he gets in to work today and see what he thinks. I might just give in and purchase an OR-Y.

i got this EXACT problem. replaced the plugs and wires. no luck. got a guy with a reader and we plugged it up and took it down the road and the reader said cylinder #3 misfire. so i bought a new coil and put on it. no help.

But mine will backfire a little when you put it under load. Does yours? Wouldn't this mean that it's getting the fuel, and just not igniting it? This might rule out the injector. I don't know.
I also had a mechanic clean my MAF and got it reading right. Don't understand too much about them but he said it was reading bad, but now it's reading good, and it didn't change my issue.

P.S. i have LTs with no cats.

Thanks for the info, Homer.

Let me add to this. I drove the car a few days last week. Rode the bike on Friday. Took my Jeep out on Saturday. Then yesterday I drove the car again (Put about 2 hours of driving on it). No real issues that haven't been listed above.

Then, this morning, on my way to work at 10am, the car started to idle like shit (Approx. 5 mins into the drive, while sitting at a light). It sounded like it was missing. I continued to drive as I was late to work ... the CEL light started to flash and it was obviously misfiring, but was not driving horribly bad. Again, didn't want to stop since I was late to work. After approximately 5-10 minutes of highway driving the CEL light stopped flashing and the miss was gone. I drove the rest of the way to work (Approx. 15 minutes) without issue. I'm going to grab the OBD reader now to see what code it's throwing...

New codes are:
P0300 - Random misfire detected
P0140 - o2 circuit blah blah (from when I disconnected the o2 sensor)

Replace the plugs and wires then get back to us

It's on the list. This weekend I'm doing a steering box, sway bar disco's and other crap on the Jeep. I need to thin the heard... one of the TA's needs to go, and possibly the bike...

What's everyone's favorite plugs and wires? NGK on plugs and GM Performance, DUI, Moroso, MSD, etc.?

My Vengeance wires and NGK V-Power plugs showed up today. Would have preferred Iridiums over platinum, but it is what it is. Will try to get them installed on Friday. Any recommendations on specific tools required over the average wrench, socket, etc.?

http://pafirefighter11.smugmug.com/Automotive/Automotive-Photography/i-QfFgRGt/0/XL/IMAG0059-XL.jpg

Okay, changed out the plugs and wires. What a PITA!! I had half NGK and half other brand plugs. Odd. They were gapped to .085!

http://pafirefighter11.smugmug.com/photos/i-kLNnwFP/1/L/i-kLNnwFP-L.jpg

http://pafirefighter11.smugmug.com/photos/i-bCMPT8c/0/L/i-bCMPT8c-L.jpg

It started up and ran smooth at idle. No issues. Then I took it out for a drive. Got on it a bit under 40 MPH, again fine. Hit the highway and the SES light started flashing - misfire. I disconnected the driver side front o2 and did the same. Same issue. Plugged the driver side back in, then unplugged the pass. side. It ran great for a bit 'til I got it about 5 minutes down the highway, then it started doing the SES blink and misfire.

Any other ideas?

Drove to my buddies. He is a mechanic for UPS. It was approx. a 35 minute drive. Car was fine for 3 minutes then went to misfire. It mainly misfires above 25 MPH, typically in the higher gears and higher RPMs. On the highway it's almost a constant misfire (CEL blinking) until I drop down below 25 MPH and then eventually it stops blinking, though I still feel the misfire.

Checked the passenger side cat - it's okay. Didn't get a chance to check driver side cat. We did check both cats with my g/f's infrared thermometer. Driver side was 475, passenger side 375. Between the front/back of the cats it was only approx. 40-60* max. Here's where things get odd though...

We figured we would test the injectors, coil packs, etc. While the car was running we pulled one injector (the wiring obviously) at a time. Each injector, when unplugged, caused the motor to drop and run worse than it already was. That was, until we got to cylinder 5. When we pulled the plug on cylinder 5, nothing happened. We swapped coil packs quick to see if it was related to the coil. The problem did not move.

We swapped the #5 injector to a Ford injector that was the same clip/setup, just to see what happened. Started up the car and my CEL turned off. (It's showing a P0420 for the o2, and a random cylinder misfire btw). The problem got worse. We put the stock injector back in to #5. CEL came back on.

Ohmed out the injectors. All were around 13.1, though on cylinder 5 we had a a reading of 14.2 and also 13.2.

I drove to Pep Boys just to get some Sea Foam for S&G's. Left my buddies, drove the 5 minutes there. Car drove like shit. Went inside, no Sea Foam, came out. Started the car and it drove perfect for about 5 minutes. Then back into crap. 10 more minutes and I was at Advance Auto. Went in, got Sea Foam, came back outside. Car drove great for 5 more minutes, then back to crap again.

Bad injector? Something internal? Something else?? I just sold my Jeep and it's too cold for the bike so I NEED to get this car up and running as it's my DD now 'til I pick up a new Jeep. Thanks...

Wish i could help!

I appreciate that. I'm so sick of this car... It's back to being my DD for this week 'til I pick up my new Jeep.

Here's a quick cell phone video of some revs and idle - I can take other videos as needed and use the GoPro. I just unplugged the AIR fuse and relay (Since my system is missing due to the prior owner) then started it up like this:

http://www.youtube.com/watch?v=_n_8yLhQNtU

Local shop hooked it up to their diagnostic laptop. Driver side, front o2 is bad. Got it in the mail yesterday. Will try to install it today at lunch time. The shop said he does not believe the o2 is causing the misfires though. I'm hoping it is, but we shall see...

I replaced the front driver side o2, recet ECU. Runs better, not the fix though. It has some weird electrical things going on. Shifted into reverse and the speedo jumped to 20 MPH. Opened the cutout and the RPM's jumped 300 RPM. 2 weeks ago the speedo was reading WAY low. 42 MPH when doing 70 for example.

Did you ever get this resolved?

Yeah just wondering also, mine sounds similar.

Nope. Next is going to be checking grounds and wiring some more...

Just wanted to update the latest. My buddy and I at work checked the wires running from the PCM to the coils. They all have continuity per our multi-meter. So, the wires are good from the PCM to the coils. One more thing ruled out I guess....

I would definitely clean all your grounds. What kind of voltage are you seeing when the car is running?

Voltage is normal. Right around 14.4 while running. Battery is 12.1 or so when off. We checked and the motor is ground very well. I need to physically see if the grounding straps on the rear of the block are good. What's the best way to get a visual?!

Ever consider pulling the valve covers and looking at the valve springs or doing a compression test?

Ever consider pulling the valve covers and looking at the valve springs or doing a compression test?

The only reason I haven't gone that route is that it runs great sometimes and doesn't other times (Hot or cold). To me that rules out a mechanical problem.

The only reason I haven't gone that route is that it runs great sometimes and doesn't other times (Hot or cold). To me that rules out a mechanical problem.

Spray some carb cleaner around the intake and see if your idle changes. Might have bad intake gaskets causing the PO300.

Don't know if any of the Ford F 150 problems would maybe be the same as yours. But my truck had symtoms kinda like yours. And it was a coil pack. They said sometimes also Cracked eletronic firing sensor or throttle position sensor or Fuel pump control module.Don't know if this will help just a thought after reading your problem.That mystery stuff is the worst crap!

Sorry just watched your little video and mine was'nt like that, mine only missed when under a load 45-65 mph. Other wise cruising down highway at steady speed no problem and would idle smooth. But start to go up hill and step on pedal it would feel like misfire or like torque converter not working or something.If you took it out of overdrive it would go away even under load.

That is a horrible dead miss. I didn't see the video before my earlier post. You need to do a compression check on at least cylinder 5. Or at least pull the valve cover.

Thanks fella's. I'll do some more looking and a compression test soon, as well as carb cleaner spraying for vacuum leaks.

I dropped it off at another local shop today. They put some time into it and are going to put some more work into it next week.

Just some info from my Torque app...

Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 6.667 %
Engine Coolant Temperature = 197.6 °F
Fuel Trim Bank 1 Short Term = 16.406 %
Fuel Trim Bank 1 Long Term = 24.219 %
Fuel Trim Bank 2 Short Term = -5.469 %
Fuel Trim Bank 2 Long Term = 13.281 %
Intake Manifold Pressure = 6.382 psi
Engine RPM = 1,608.25 rpm
Speed (OBD) = 34.797 mph
Mass Air Flow Rate = 155.214 cfm
Throttle Position(Manifold) = 11.373 %

End of report.

41* timing advance?!
http://pafirefighter11.smugmug.com/Automotive/1998-Pontiac-Trans-Am/i-N2rbV4m/0/L/487345_10151269396016080_705252989_n-L.jpg

Freeze frame information @ idle:

------------------
Fuel Status = 0 byte
Engine Load = 2.353 %
Engine Coolant Temperature = 226.4 °F
Fuel Trim Bank 1 Short Term = -10.938 %
Fuel Trim Bank 1 Long Term = -7.812 %
Fuel Trim Bank 2 Short Term = -14.844 %
Fuel Trim Bank 2 Long Term = -8.594 %
Intake Manifold Pressure = 6.382 psi
Engine RPM = 755.5 rpm
Speed (OBD) = 0 mph
Mass Air Flow Rate = 53.824 cfm
Throttle Position(Manifold) = 0.392 %
End of report.

Per Tom Oates:
http://pafirefighter11.smugmug.com/photos/i-kjpLGwC/0/XL/i-kjpLGwC-XL.jpg

I had similar issues with my previous M6. Have you checked fuses? Mine ended up being the 20A "ENG SEN" fuse in one of the boxes under the hood.

So if you're just reading this, #5 and #7 are the misfiring cylinders.

I purchased a compression tester today:
http://pafirefighter11.smugmug.com/photos/i-nG5D8Bc/0/XL/i-nG5D8Bc-XL.jpg

Only had time to do 4 cylinders, but everything checked out fine:
http://pafirefighter11.smugmug.com/photos/i-hVqTDN4/1/XL/i-hVqTDN4-XL.jpg

And the plugs ... 1-3-5-7:
http://pafirefighter11.smugmug.com/photos/i-2DFpjGR/0/XL/i-2DFpjGR-XL.jpg

I don't know what Mode $06 test results are but here are mine:

Mode $06 report generated by Torque for Android
================================================

Vehicle VIN: Not present
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: Not present

Unit and scaling information are not supplied with the data from the ECU for this type of vehicle. Consulting the manufacturers service book for this information is recommended.

Test report:
------------------
TID:$02 CID:$04
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$10
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$11
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$12
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$20
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$21
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$26
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$30
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$31
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$36
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$40
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$46
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$04 CID:$20
- High sensor Voltage for switch time calculation
Max: 32,766
Test result value: 32,770
FAIL
----
TID:$04 CID:$30
- High sensor Voltage for switch time calculation
Max: 32,766
Test result value: 32,770
FAIL
----
TID:$06 CID:$35
- Lean to Rich sensor switch time(calculated)
Max: 62
Test result value: 19
PASS
----
TID:$06 CID:$41
- Lean to Rich sensor switch time(calculated)
Max: 104
Test result value: 35
PASS
----
TID:$06 CID:$55
- Lean to Rich sensor switch time(calculated)
Max: 67
Test result value: 42
PASS
----
TID:$06 CID:$61
- Lean to Rich sensor switch time(calculated)
Max: 106
Test result value: 50
PASS
----
TID:$07 CID:$0c
- Minimum sensor Voltage for test cycle(calculated)
Max: 0
Test result value: 65,491
FAIL
----
TID:$07 CID:$0d
- Minimum sensor Voltage for test cycle(calculated)
Max: 1
Test result value: 65,491
FAIL
----
TID:$02 CID:$04
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$10
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$11
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$12
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$20
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$21
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$26
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$30
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$31
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$36
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$40
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$02 CID:$46
- Lean to Rich sensor threshold voltage(constant)
Test incomplete or dependant test failed
--
TID:$04 CID:$20
- High sensor Voltage for switch time calculation
Max: 32,766
Test result value: 32,770
FAIL
----
TID:$04 CID:$30
- High sensor Voltage for switch time calculation
Max: 32,766
Test result value: 32,770
FAIL
----
TID:$06 CID:$35
- Lean to Rich sensor switch time(calculated)
Max: 62
Test result value: 19
PASS
----
TID:$06 CID:$41
- Lean to Rich sensor switch time(calculated)
Max: 104
Test result value: 35
PASS
----
TID:$06 CID:$55
- Lean to Rich sensor switch time(calculated)
Max: 67
Test result value: 42
PASS
----
TID:$06 CID:$61
- Lean to Rich sensor switch time(calculated)
Max: 106
Test result value: 50
PASS
----
TID:$07 CID:$0c
- Minimum sensor Voltage for test cycle(calculated)
Max: 0
Test result value: 65,491
FAIL
----
TID:$07 CID:$0d
- Minimum sensor Voltage for test cycle(calculated)
Max: 1
Test result value: 65,491
FAIL
----

End of report.

Took it to a fellow LS1 owner. He hooked it up to his EFI Live. He stated: "I hooked up HPtuners and monitored current misfires and #5 and #7 are misfiring badly. It sounds like to me he's either got a broken valve spring, or two, or a bent valve. I told him to get the driver's side valve cover off asap and see what's up before he does anything else. "

Took it to a fellow LS1 owner. He hooked it up to his EFI Live. He stated: "I hooked up HPtuners and monitored current misfires and #5 and #7 are misfiring badly. It sounds like to me he's either got a broken valve spring, or two, or a bent valve. I told him to get the driver's side valve cover off asap and see what's up before he does anything else. "

Time to get at it then. A couple of people have mentioned that in this thread including myself. If you have swapped coils, wires, new plugs and checked for power at those (and injectors) then it is time to test the mechanical aspect.

I would start with either a compression check or pull the valve cover and visibly inspect for broken springs.

Time to get at it then. A couple of people have mentioned that in this thread including myself. If you have swapped coils, wires, new plugs and checked for power at those (and injectors) then it is time to test the mechanical aspect.

I would start with either a compression check or pull the valve cover and visibly inspect for broken springs.

Yep, I'm hoping it's a valve spring!

Read post #44 - RE: Compression.

Okay, photos of the valve springs:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-g2zvPxF/0/XL/IMAG0156-XL.jpg

7:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-JF2nzrN/0/XL/IMAG0158-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-RgkBnkT/0/XL/IMAG0163-XL.jpg

5:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-THtNQVR/0/XL/IMAG0164-XL.jpg

3:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-Gr3wj7j/0/XL/IMAG0165-XL.jpg

1:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-8cnZX4M/0/XL/IMAG0166-XL.jpg

Valve cover:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-NqKPV2r/0/XL/IMAG0167-XL.jpg

Finally got to #8. Nasty:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-mCsQBLs/0/XL/IMAG0173-XL.jpg

Runs better, drives better, but still misfires on #5 & #7.

UPDATE: SO, I think I may have found the issue, or a big part of it. I decided today to check things I have checked already, just in case I missed something, or see if anything changed. On my way home I stopped, unplugged the MAF, reset the codes on the PCM with my Torque app, and drove. WOW.... what a difference. CEL is not blinking, it's not even on anymore. I drove it 25 miles home. The car still has minor hesitation but no big misfire. Check out these screen shots:

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-cnMvCnt/1/O/screenshot.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-cWvXsWh/1/O/screenshot.jpg

I'll order up a new MAF and see if that fixes things completely!

Random question... I know carb cleaner is obviously flammable but should it catch fire when spraying it on the engine compartment? lol. I mean, that's a sign of a spark somewhere it shouldn't be, right? The motor wasn't really hot when I sprayed it either...

You probably need a spark, depending on the chemical, but
http://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html

there are other sources of spark in an engine bay besides the spark plugs. The alternator has a lot of that going on, for example. You could have vapor start to flash in the alternator and spread to a spill site in another place.

Just going throw this out there, but my car did sorta the same thing. Found out it was 2 leaky injector o-rings. Hope you get!

You probably need a spark, depending on the chemical, but
http://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html

there are other sources of spark in an engine bay besides the spark plugs. The alternator has a lot of that going on, for example. You could have vapor start to flash in the alternator and spread to a spill site in another place.

I grabbed some CRC carb cleaner:
http://www.shopthedude.com/filedb/5/9/18095.png

It ignited on the passenger side, near the PCV hose and also off the manifold/coil pack area (Generic shot I edited with the arrows):
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-d5L2s76/0/L/LS1Fire-L.png



Just going throw this out there, but my car did sorta the same thing. Found out it was 2 leaky injector o-rings. Hope you get!

Thanks! How did you verify the leaking o-rings? I've swapped in other injectors (With different o-rings) and still have the same issue. No leaks I can see either.

I wonder if the coil packs or static electricity could do it? I can't imagine that a stray spark would be related to this problem.

I smelled fuel really, then took a closer look at all the orings around the injectors and saw that I had nicks on two injectors

Thanks, man. No fuel smell in the engine compartment.

I'm at the point where I am driving a Ford now... '13 "Gotta Have It" Green... I'm going crazy...

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-VPg4KSK/0/XL/IMAG0210-XL.jpg

It's kind of nice driving a comfortable, reliable vehicle...

Just an update. No new news...

Just an update. No new news...

PM me if you want to sell her. Pass your headache on to someone else haha.

PM me if you want to sell her. Pass your headache on to someone else haha.

Still making payments on the damn thing LOL. My '01 will be for sale soon once I change out the head gaskets.

I'll take a new video shortly. It runs a LOT better than it did in that video I posted, mainly 'cause I disconnected the MAF. Weird.

So Steve83ta has been super generous and took a look at the car for me yesterday. After a couple hours of messing with different things on the car there's something to think about related to fuel:

On his '98 TA pressure is 60 psi at start, stays at 60 when revving, drops to 50 when turned off, stays at 50 for several hours.

On my '98 TA pressure is 52 psi at start, stays at 52 when revving, drops to 0 within 1-2 seconds when turned off.

We checked the injectors, they are not leaking. He thinks it could be the fuel pump causing the immediate drop in psi when the motor is turned off. We're going to do the filter today (I haven't changed it while I've owned the car), check the fuel pump amperage draw, etc. If the amps are not within spec (And maybe even if they are) I'll be looking at purchasing a new fuel pump next week.

Good luck! My '99 SS also has 52 psi with power to the pump, but I never checked to see how long pressure held after key off.

Have you tried spraying carb cleaner around the intake to see if idle changes? If you have a bad enough leak it can cause the misfires. Although you should get a "system too lean" code.

Also, I think you mentioned the car runs better with the MAF unplugged? Have you tried replacing it with a good one?

We have run 4 different MAF's (all confirmed working) through the car. No change. I used carb cleaner and it ignited. Never seen that happen before, but it did. Brake clean didn't cause any change as Steve had it hooked up to his scan tool with the graphing program open to look for changes.

He tested the fuel pump. Amps are around 7.5, which is just about what his '98 is at. Also, volume of fuel is a bit more than his is flowing, so the fuel pump isn't the main issue. Changed the fuel filter, no change in drive-ability.

Checked vacuum. -15 or so, and bouncing all over the place. Goes up to around 15-20 when on the gas, but again it's bouncing and not consistent. Per his tech book it's stating this could be a burnt valve, broken valve spring, etc. We're going to do a compression check again (this time on the passenger side cylinders) and possibly rip apart the top end this week I think.

PROBLEM FOUND! Check the photos for the work done today... All are cell photos so the quality sucks:

Went to do a compression check:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-54nPSt3/0/XL/IMAG0383-XL.jpg

Then decided to pull the valve covers - passenger side:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-S9CrqkR/0/XL/IMAG0384-XL.jpg

A little closer:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-P5c9bVQ/0/XL/IMAG0388-XL.jpg

Time to rip the top end apart:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-chGJrTP/0/XL/IMAG0390-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-3BmwmWL/0/XL/IMAG0395-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-JxVLnr3/0/XL/IMAG0397-XL.jpg

Steve has his old LS1 with 55k miles on it (He has his LS6 now) so we're using his heads, springs, rockers, etc:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-4GvXqrt/0/XL/IMAG0391-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-tGtWjH9/0/XL/IMAG0392-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-VRJcGGg/0/XL/IMAG0393-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-s3MxzTB/0/XL/IMAG0394-XL.jpg

We're hoping to have the heads and everything swapped over by Saturday or Sunday at the latest. We ordered all the gaskets needed from GM today. Should be here tomorrow or Saturday. I can't wait to get this thing back on the road!

Nice thread update Rick. I tried to update the other Ls1 thread but it kept screwing with my pic sizes.

I hope thats answers a lot of peoples questions. Like I said on another thread, the guys who had that in the back of your mind give yourself a good pat on the back. For the others, well its a learning experence and we we're greatfull for all kinds of ideas, there is never a dumb one, that can often lead to the eureka moment, getting the job done. Now back together, and a FUN BURNOUT!!

Steve

PROBLEM FOUND! Check the photos for the work done today... All are cell photos so the quality sucks:

Went to do a compression check:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-54nPSt3/0/XL/IMAG0383-XL.jpg

Then decided to pull the valve covers - passenger side:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-S9CrqkR/0/XL/IMAG0384-XL.jpg

A little closer:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-P5c9bVQ/0/XL/IMAG0388-XL.jpg

Time to rip the top end apart:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-chGJrTP/0/XL/IMAG0390-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-3BmwmWL/0/XL/IMAG0395-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-JxVLnr3/0/XL/IMAG0397-XL.jpg

Steve has his old LS1 with 55k miles on it (He has his LS6 now) so we're using his heads, springs, rockers, etc:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-4GvXqrt/0/XL/IMAG0391-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-tGtWjH9/0/XL/IMAG0392-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-VRJcGGg/0/XL/IMAG0393-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-s3MxzTB/0/XL/IMAG0394-XL.jpg

We're hoping to have the heads and everything swapped over by Saturday or Sunday at the latest. We ordered all the gaskets needed from GM today. Should be here tomorrow or Saturday. I can't wait to get this thing back on the road!


Glad you found the issue but pretty sure myself and a couple others posted to check the valvetrain on the first or second page of this thread...?

Anyways, hope everything works out as you've been having this issue for quite some time.

Just throwing this out there... Does this look like a cracked rocker?

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-kM3RRBK/0/XL/Rocker-Close-XL.png

Just throwing this out there... Does this look like a cracked rocker?

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-kM3RRBK/0/XL/Rocker-Close-XL.png

You made me stop and doubt myself thinking I was also blind. I went out and checked. It has to be a refection from the LED flashlight and camera flash because it isn't cracked. There is a casting step there.... Unless Im still blind. You can't happen to tell me what cylinder that was on the passenger side can you?

Glad you found the issue but pretty sure myself and a couple others posted to check the valvetrain on the first or second page of this thread...?

Anyways, hope everything works out as you've been having this issue for quite some time.

Your right Lt1pwr1, I wasn't involved in this thread untill last Thursday. I stumbled on this thread though another thread and relized Rick lived in my town and I never had met him, and he works 3 mins from my house. Small world. I reached out, told him about myself and I could get that thing right. Thats why Im giving credit where credit is due. I know it was mentioned somewhere either on this thread or one of the others there is on it. But I wasn't going to pull everything apart for fun. Had a diag session with Rick last week and I new on Sunday it was a broken valve spring or burned valve, and that was without pulling a bolt off the car. A vacume gauge can do wonders if you know what your looking at and have the knowledge.

If you had that in the back of your mind or mentioned it eairler in the thread impressive since it was a "web Diag". :hail:

Again thanks for eveyones input. In the future if someone ever has the same kind of symptoms they have this thread to refer to.


Small Update

Lt1pwr1 I went back and reread the whole thread, I had only skimed it before I got involved. And saw you said pull the covers way back in Feb, then again in March. Along with offering to take the headache off his hands. Sounds like you know at least as much as me ;)

Ill know more tomorrow, but one odd thing about this was the amount of missfires on 5-7 and the plugs are completly fouled out after a couple thousand miles. Some of this could be becuase of the broken spring, but that spring is on the pasenger side, cylinder #8 intake spring. One of the first things I noticed when I hooked up my scan tool was the LTFT was at 126% as you are prob well aware that is WAY WAY OUT RICH! Some plugs did okay and looked perfect with this way extra fuel so the car didn't lean itself out and burn up, cylinders 5 & 7 did not! Like I said completly fouled. Im hoping this was becuase of the extra fuel but most of me doesn't buy it, also the MAF was unplugged for an extend time so that didn't help either. Thats why Rick and I are doing both heads. Just in case.

Rick did a great job with the pics and the step by step so I let this tread run a little bit, but this the other info I posted on LS1.com on Thursday.

05/9/13

"I don't want to threadjack Rick's thread but I figured I would give you a guys an update as we said answers would be today. And for everyone who agreed and said "Broken Valve spring, or burned valve" give yourself a good pat of the back as you were right. Broken Valve spring and pics to follow. And for everyone else thanks for all of your ideas. Also on a side note. Some one has been inside this engine, how do I know, the driver side valve springs, retainers and keepers are stock, the passengers however are not, see if you can tell in the photos I post. Rick might have some better ones. This is also a BIG NO NO!! That is getting corrected also.

https://imageshack.us/a/img690/1102/007wkl.jpg
https://imageshack.us/a/img41/8756/008jn.jpg

Another huge shout out to Steve for all the help today! The rocker is not cracked. Strange optical illusion I guess. More progress today. Heads are off, everything is cleaned, getting ready to put the new heads on... Photos from today:

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-PjDSMwx/0/XL/IMAG0405-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-hFX7jBj/0/XL/IMAG0407-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-c3xQpMk/0/XL/IMAG0408-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-jnZ3H8j/0/XL/IMAG0410-XL.jpg

Oh haiii... Found 2 of these - of course we didn't verify which cylinder(s) they were from:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-vtsLjZP/0/XL/IMAG0412-XL.jpg

Looks like aftermarket springs, retainers... Possibly a head off of a newer Trans Am, Corvette, etc.?
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-GRLBNDv/0/XL/IMAG0413-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-nXMStrB/0/XL/IMAG0414-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-QLSjfTV/0/XL/IMAG0415-XL.jpg

Heads are going back on tomorrow or during the week (depending on family plans).

And a couple non-cell phone shots with my Nikon D2x and Tamron 17-55 f/2.8:

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-r8rsHsb/0/XL/BCM_7828-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-bszQJQ3/0/XL/BCM_7825-XL.jpg

Thanks again to Steve for all the help last night!

Some progress shots:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-FvDxXJg/0/XL/IMAG0424-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-XssPzDJ/0/XL/IMAG0425-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-d7LT6z7/0/XL/IMAG0426-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-SXXbP2j/0/XL/IMAG0427-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-pv3V6HC/0/XL/IMAG0430-XL.jpg

SHE RUNS!!

Video here:
Rebirth of my 1998 Trans Am! - YouTube


Some more progress (cell phone) shots from yesterday:

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-9JMkDs5/0/XL/IMAG0433-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-4KWf72J/0/XL/IMAG0435-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-rzMZbcF/0/XL/IMAG0436-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-WWddcvk/0/XL/IMAG0437-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-93XDhJv/0/XL/IMAG0438-XL.jpg

Bolting the exhaust back together:
http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-NWKP4kN/0/XL/IMAG0440-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-kjBLXvz/0/XL/IMAG0441-XL.jpg

http://pafirefighter11.smugmug.com/Automotive/98-Trans-Am-Misfire/i-kDcwCPk/0/XL/IMAG0442-XL.jpg

We still need to add some coolant and a coolant temp. sensor.

"]http://youtu.be/W6KrBrPtNhI"]
An additional Vid of Ricks engine running in the daylight. Some of the backround noise is from the loud K&N open air filter.

I'll have another vid up soon which combines this and a smoking vid I took lol.

Video from yesterday of intake & engine area, and exhaust (Burning up some oil! No longer smokes though):
1998 Pontiac Firebird Trans Am WS7 - First Long Idle - Daytime Video - YouTube

One last vid to this epic long thread.

Since I can't stand the vid of the exhaust burning all the oil and coolant that ran down the Y-Pipe after its first start up, here is a vid of it running after a good 15 mile test drive.

http://youtu.be/dQgQEhnIU88