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Old 04-03-2007, 09:41 PM   #1
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Default LT1 Running Rough / Reduced Power / Poor Mileage / NO DTC CODES

All -

I posted this in the LT1 area, but I thought maybe you PCM tuners might be able to dismantle this driveablity problem, here are the specifics:

This is what my car is doing; about 6 weeks ago my LT1 / M6 Firebird started to run rough. I'm an engineer who was with GM back when the Tech 2 was being developed (I was a transmission calibration engineer) and, to me, the old LT1 seemed like it was running in open loop or something along those lines. Poor gas mileage, slightly rougher idle than normal (FYI, it has an LT4 Hot Cam kit) and reduced power thru the entire RPM range. It never broke up at the top end, but it just didn't feel 'strong'. Driving along at low RPMs in sixth gear was now painful too; it would shudder and shake in 6th below 2k - something was not right. No codes though... I was perplexed.

I didn't have access to a real scan tool, so I started guessing at would could be the issue; I replaced all 4 of the O2 sensors and the Engine Coolant Temp (ECT) sensor, the one in the water pump, not the one in the radiator (for the gauge) - No change.

I purchased some OBD II S/W and a ELM 327 H/W interface (over the net) but before I rec'd it, I got a job in NC and had to leave my family in Detroit. My wife doesn't drive a stick, so I couldn't leave this car for her. With great trepidation, I headed off for NC in the bird.

The vehicle drove, just not very well, like 85% or so. I hoped the 600 mile trip would finally set a hard code so I could drop by Autozone and have them tell me "You've got a <insert your favorite driveability problem here> code". I never got any DTCs. (drat!)

So, again, I started guessing; the Opti was only 20K miles old, but it was a stock GM replacement. My MSD box (6 BTM, for blowers and turbos with boost retard - the car is still N/A [I have not installed the STS yet] but the MSD still helps), plugs, wires, and MSD coil were also all about 20K miles old too. I considered trying to drive home on Easter weekend and replacing the Opti with a billet MSD unit, but (as I was driving from my new office off to lunch) my car died going up a hill. It was towed to a local Pontiac dealer in greensboro last week Thursday.

Today, the technician said he could only communicate with the vehicle via the Tech 2 for about 30 seconds before communication would cease. According to them, that happened 2 times. They wanted to through a PCM at it, but that would wipe away all improvements I've got from Bryan Herter and PCM 4 Less, and it might not help the car in its current configuration.

I don't know what to do, so I sent the PCM back to Bryan Herter, and he told me (off the top of his head) that I needed an O2 sensor - except I replaced ALL of them as a first fix. He thinks the PCM might be at fault, but the reason for my post is to ask for any additional insight from this community.

Has anyone else ever had a similar problem? What was the resolution?

Let me know if you have any suggestions - Thanks!

Mike Eldridge (great421@yahoo.com / 313 268 7931 Cell)
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Old 04-06-2007, 07:45 AM   #2
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If you have a few common tools, check this http://shbox.com/ignsw/ign_switch_repl.html
before you go any further with parts. This won't cost you anything other than an hour or two. You don't *Have* to drop the steering mast. I replaced my switch by just dropping the "V" support(two 10mm nuts) and the main support nuts (two 14mm nuts) and the three 10mm bolts at the foot of the mast. I could then access the 2 small bolts and single phillips screw retaining the switch.
I just went thru this last week. Mine was running poorly for a few days, then died in a grocery store parking lot. The replacement is $12 at most Autozones, O'Riellys, etc. I hope it's something this simple for you.
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Old 04-06-2007, 08:37 AM   #3
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Default

Just "fixed" a 93, showing the same symptoms...
Pull the vac reference line off the FP reg. Fuel squirting out?
The owner went thru all the "replace parts" exercizes, and found the engine was in the same condition, after spending $1k.
I was asked to check the FP. When I hooked up, and pulled the vac, WALA!! The FPR was acting as a 9th inj! Replaced it, and mileage is back to 20, and everyone is "happy"...
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Old 04-06-2007, 08:55 AM   #4
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Default

Quote:
Originally Posted by Old Geezer
Just "fixed" a 93, showing the same symptoms...
Pull the vac reference line off the FP reg. Fuel squirting out?
The owner went thru all the "replace parts" exercizes, and found the engine was in the same condition, after spending $1k.
I was asked to check the FP. When I hooked up, and pulled the vac, WALA!! The FPR was acting as a 9th inj! Replaced it, and mileage is back to 20, and everyone is "happy"...
Where is the vac reference line at?? Bc right now my car is getting horrible gas mileage.. But i do have a MASSIVE exhaust leak at the flange..
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Old 04-06-2007, 09:24 AM   #5
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Exclamation The

Vac line is on the FPR. Pull it off, and see WTF is there. Gas??
As for the exh leak.. that could be raising havoc with the O2 sensor accuracy. FIX IT, and go from there on the T/S process. Til then, U R just "pounding sand in a rat hole"..
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Old 04-15-2007, 03:18 PM   #6
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mightyquickz28 -

So, a faulty ignition switch was causing your vehicle to run poorly?

Thanks for the info; when I get my car back from the dealer, I'll check it out.

BTW - I did have this type of problem w/ my Sable about 15 years ago, but when it went bad, it melted completely!

MIKE

Quote:
Originally Posted by mightyquickz28
If you have a few common tools, check this http://shbox.com/ignsw/ign_switch_repl.html
before you go any further with parts. This won't cost you anything other than an hour or two. You don't *Have* to drop the steering mast. I replaced my switch by just dropping the "V" support(two 10mm nuts) and the main support nuts (two 14mm nuts) and the three 10mm bolts at the foot of the mast. I could then access the 2 small bolts and single phillips screw retaining the switch.
I just went thru this last week. Mine was running poorly for a few days, then died in a grocery store parking lot. The replacement is $12 at most Autozones, O'Riellys, etc. I hope it's something this simple for you.
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Old 04-15-2007, 03:24 PM   #7
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Old Geezer -

OK, that is quite easy to check. If it is the stock FPR BTW, then I have an adjustable unit on the bench that I was planning on installing when I put in the new injectors and STS on, but if that will fix this problem, I'll put it on early!

Question though; what's the stock FP regulator set at?

MIKE

PS - 1954?!?! I was negative 12 years old in 1954! Thanks for the advice!

Quote:
Originally Posted by Old Geezer
Just "fixed" a 93, showing the same symptoms...
Pull the vac reference line off the FP reg. Fuel squirting out?
The owner went thru all the "replace parts" exercizes, and found the engine was in the same condition, after spending $1k.

I was asked to check the FP. When I hooked up, and pulled the vac, WALA!! The FPR was acting as a 9th inj! Replaced it, and mileage is back to 20, and everyone is "happy"...

Last edited by great421; 04-15-2007 at 03:29 PM..
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Old 04-15-2007, 04:08 PM   #8
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Bwaaahaaahaaa.. Negative 12 in relation to OG? Then you were negative 14 on my birthday.

Quote:
Originally Posted by great421
Old Geezer -

OK, that is quite easy to check. If it is the stock FPR BTW, then I have an adjustable unit on the bench that I was planning on installing when I put in the new injectors and STS on, but if that will fix this problem, I'll put it on early!

Question though; what's the stock FP regulator set at?

MIKE

PS - 1954?!?! I was negative 12 years old in 1954! Thanks for the advice!
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Old 04-18-2007, 06:04 AM   #9
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Quick Update:

The new PCM has not been installed yet at the dealership; their tech "is really over-booked". NC is not like Detroit at all. In Detroit they would have been done with this in a day max - not 3 weeks (and counting)!
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Old 04-19-2007, 05:04 PM   #10
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Quick Update 2 -

New PCM is in; still runs the same. Dealer Tech says "replace the cats". Quoted price: $1400!!!!!!

I asked, what if this doesn't solve my problem, do I get my $1400 back? (No, was the reply.) So, again, I look to you folks for suggestions.

Oh, and I've already looked at Summit for cats; $350 for a whole new Magnaflow 2-piece y-pipe with high flow cats; yes, it's already been ordered...

MIKE
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Old 04-19-2007, 06:22 PM   #11
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I would not recommend gutting the cats to get rid of the blockage. I performed this un-recommended technique and the car ran great. I certainly can't recommend drilling a quarter inch hole in each cat(if you have a 96/97 for example), then taking a Phillips screwdriver and ramming it into the inside, dislodging all the interior so that it could be blown out the back of the exhaust. This clears, or guts, the cat and is not recommended since paying $1,400 is vastly preferable to not paying a dime and living with gutted cats. Oh... I would not recommend placing a sheet metal screw of the appropriate size in the quarter inch hole mentioned above to seal the hole shut.
Signed, "Honest Dave".


Quote:
Originally Posted by great421
Quick Update 2 -

New PCM is in; still runs the same. Dealer Tech says "replace the cats". Quoted price: $1400!!!!!!

I asked, what if this doesn't solve my problem, do I get my $1400 back? (No, was the reply.) So, again, I look to you folks for suggestions.

Oh, and I've already looked at Summit for cats; $350 for a whole new Magnaflow 2-piece y-pipe with high flow cats; yes, it's already been ordered...

MIKE
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Old 04-20-2007, 11:35 PM   #12
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Default Honest Mike

Dave - I hear you!

I did (not) do this very same (un-modification) back in the late 80s with a 5 door Citation (I loved that car!). Once I fit a 7 foot sofa in the back of it - Amazing.

Anyway, "Honest Dave", if I had a place and / or the tools I'd do that very same (un)modification again, but, at this point in time, I'm living at an 'Extended Stay America' down here in Greensboro NC, so I am at the mercy of the service shops in the area.

One muffler place told me they'd replace my stock parts with the units I rec'd from Summit when they arrived, so I'm looking at about 2 hours labor (1 off / 1 on) to make this happen.

I'll keep everyone informed. I really hope this resolves the issue!

BTW - The dealer tech told me today that cylinders 2,4,6, and 8 are all misfiring / not firing, but they are indeed getting spark; therefore, it must be a clogged converter.

Additionally, I already replaced all four of the O2 sensors AND had my PCM reprogrammed (again!) by PCM 4 Less; so if I just gutted the old cats, I'd need the O2 sensor codes disabled thru another reprogramming cycle. So, I'll have the stock cats and y-pipe replaced with a pair of MagnaFlow parts and hope for the best!

MIKE

Quote:
Originally Posted by mightyquickz28
I would not recommend gutting the cats to get rid of the blockage. I performed this un-recommended technique and the car ran great. I certainly can't recommend drilling a quarter inch hole in each cat(if you have a 96/97 for example), then taking a Phillips screwdriver and ramming it into the inside, dislodging all the interior so that it could be blown out the back of the exhaust. This clears, or guts, the cat and is not recommended since paying $1,400 is vastly preferable to not paying a dime and living with gutted cats. Oh... I would not recommend placing a sheet metal screw of the appropriate size in the quarter inch hole mentioned above to seal the hole shut.

Signed, "Honest Dave".
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Old 04-25-2007, 07:05 PM   #13
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Default Update - Misfire Codes!

OK,

The Tech replaced the stock y-pipe with a unit from MagnaFlow - No change in the way the vehicle performed! Arrggghhhh!!!!! (I'm glad I didn't spend the $1400 GM wanted for their parts!)

Anyway, the car is now getting pass side misfire codes on cylinders 2,4,6 and 8.

I'm pretty sure the Opti would not discriminate and just crap out on one set of four cylinders and leave the other four alone, so all I can think of is the pass side fuel rail being obstructed - does anyone else have any guesses?

It has been one month since my car entered the dealership, and they still can't fix it! I'd really appreciate any assistance - Thanks!

MIKE
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Old 04-25-2007, 09:03 PM   #14
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I had misfire issues on my 94 with an almost new opti and the dealer had every conceivable idea and theory - none of which helped. I kept insisting "check the opti." Finally they did and there was bad tracking in the cap from the coil going bad.
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Old 04-26-2007, 07:13 AM   #15
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Default Bad Opti?

The Opti was my first thought, but they maintain that it is working properly. What could cause one bank of cylinders to misfire but leave the other bank alone?

Quote:
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I had misfire issues on my 94 with an almost new opti and the dealer had every conceivable idea and theory - none of which helped. I kept insisting "check the opti." Finally they did and there was bad tracking in the cap from the coil going bad.
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Old 04-26-2007, 09:49 AM   #16
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Quote:
Originally Posted by great421



It has been one month since my car entered the dealership, and they still can't fix it! I'd really appreciate any assistance - Thanks!

MIKE
Do ya get the feeling they're guessing? How can they assure you the opti is working fine, if no one there is capable of properly diagnosing a problem. Ask them what their diagnostic process consists of. Ask em whos the head guesser. Then go talk to him. A month to diag a rough running car is ridiculous. Find a DIAGNOSTIC SPECIALIST.
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Old 05-01-2007, 05:16 PM   #17
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Default Problem RESOLVED!

All -

I rather think they were actually taking me for all the $$$ they thought they could...

The final problem: severed plug wires - 4 of 'em on the pass side bank.

After all of Flow Pontiac's screw-ups I was treated to "The most expensive tune up in the World": $970!!!!

They charged me over list price ($220) for the GM spark plug wires ($228) and (just for fun) all the labor for all their mis-diagnosis too (Yeah!). But, if I didn't pay, they wouldn't release the car; and as we all know possession is 9/10ths of the law, so I paid up.

I now know what it feels like to be a woman going into a dealership! I even told them what the problem was (the Opti / ignition system), but they wouldn't listen; they had to diagnose it themselves (and charge me for it too)!

OK, enough ranting - We all know that dealships look at customers as walking ATMs.

Oh, but as an added bonus, their A/C "fix" didn't work either - from the moment I drove it out, it was blowing hot!

It's really reassuring to hear the dealerships 'lead tech' saying: "Well; ...I'm just stumped!" (Really!?!?)

So, edcmat, they were either guessin' or raping this Yankee - either way, I didn't appreciate it.

MIKE

Quote:
Originally Posted by edcmat-l1
Do ya get the feeling they're guessing? How can they assure you the opti is working fine, if no one there is capable of properly diagnosing a problem. Ask them what their diagnostic process consists of. Ask em whos the head guesser. Then go talk to him. A month to diag a rough running car is ridiculous. Find a DIAGNOSTIC SPECIALIST.

Last edited by great421; 05-01-2007 at 05:26 PM.. Reason: spelling
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Old 05-01-2007, 05:38 PM   #18
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Quote:
Originally Posted by great421
All -

I rather think they were actually taking me for all the $$$ they thought they could...

The final problem: severed plug wires - 4 of 'em on the pass side bank.

After all of Flow Pontiac's screw-ups I was treated to "The most expensive tune up in the World": $970!!!!

They charged me over list price ($220) for the GM spark plug wires ($228) and (just for fun) all the labor for all their mis-diagnosis too (Yeah!). But, if I didn't pay, they wouldn't release the car; and as we all know possession is 9/10ths of the law, so I paid up.

I now know what it feels like to be a woman going into a dealership! I even told them what the problem was (the Opti / ignition system), but they wouldn't listen; they had to diagnose it themselves (and charge me for it too)!

OK, enough ranting - We all know that dealships look at customers as walking ATMs.

Oh, but as an added bonus, their A/C "fix" didn't work either - from the moment I drove it out, it was blowing hot!

It's really reassuring to hear the dealerships 'lead tech' saying: "Well; ...I'm just stumped!" (Really!?!?)

So, edcmat, they were either guessin' or raping this Yankee - either way, I didn't appreciate it.

MIKE
Thats just plain bad business. They could have handled that differently. Sorry for your experience. For something like that to stump a "lead tech", well thats pathetic. I guess hes the head guesser, and not real good at it. You ought to print this thread and take it to them. I hate hearing stories like this. It taints our industry as a whole. Some of "us" make it a mission to be the best that we can be. And then again, there's "them". And regardless of their technical shortcomings, they could have handled it differently, and maybe you wouldnt have felt like you were taken advantage of by Dufus and his band of Dufi (plural for dufuses)
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Old 05-01-2007, 05:38 PM
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