1SLwLS1

iTrader: (6)

I have an iron 408 running 11.5:1 on premium pump gas in this nice Texas heat. I have had this setup since July of last year and no issues until recently. About 3 months ago I replaced the NGK TR6 plugs (with the same) and replaced the MSD wires (with the same, I broke one while taking them off). About 3 weeks ago, I added a huge oil cooler in front of the condenser with -10 feed/return lines. Looking through the filter box, I am definitely adding more heat to the incoming air (120*F IATs at most, unless idling ~ 150*F). Everything has been fine up until about 3 weeks ago.

About 3 weeks ago when the engine had been running for a while, I went WOT in 1st and it sounded like I hit the limiter at 4500 RPMs. I was low on gas and figured maybe I had starved the pump even though its supposed to be submerged (stock). Filled up and tried again. Same issue, 4500 RPM or so, it seems like I hit the limiter or had some misfires. It would only do this after the engine had time to soak up quite a bit of heat. If it was colder, still at temp, but colder, it would run to 6K without issue. Today, when I went WOT, the engine was around 185*F, the oil around 160*F, I got some nasty popping and misfiring.

I have been using this cheap software, OBD Whiz, to log my driving (came with Bluetooth OBD Adapter). I get no MIL's, no misfires shown in the computer, nothing obviously sticking out. I attempted to calculate AFR using the MAF and fuel rates given by the software but I think it calculates fuel rate based on the MAF, so it's just a circular calculation. Everything under the hood seems OK, the plugs are tight on the coils and plugs, the wires aren't hitting the headers, no obvious signs of arcing, no obvious abrasions, nothing is unplugged or loose. What should I look for in the logs? Maybe a fouled plug? Maybe the OE fuel pump is failing and cannot supply enough fuel at 4500 WOT, although it will still pull to 6K but may be lean - need a wideband ASAP.

Side note about the fuel pump, the check valve has been busted for probably 1.5 years now. I usually have to crank for 2 seconds, stop, wait for the audible pump noise to cease, crank again and it fires right up. I haven't put any gauge on the fuel system to verify if it is actually loosing pressure over periods of sitting. If it is a hot restart, it fires right up. This occurs usually after sitting for 2+ hours.

HELP Please!


****See Post 15 for an update****

1SLwLS1

iTrader: (6)

Bump, I plan on getting a wideband and fuel pressure gauge to better monitor the system as well as to help diagnose this issue. Thoughts?

joecar

Are you getting spark knock...? Did you hear any knock/detonation...? Does your OBD Whiz log KR (Knock Retard)...?

IAT at 120°F is too hot and may be contributing to spark knock... what year/model/vehicle do you have...? If you could duct cold air your IAT will be much lower.

Can you produce a .xls file containing a log of these:
VSS
TP
RPM
MAF
MAP
IAT
ECT
SPARKADV
KR
LONGFT1/2
DYNAIR
DYNCYLAIR

I take it you got it tuned previously...?

1SLwLS1

iTrader: (6)

It's funny that you seem to be the one person that has the answers to my questions, haha.

I don't believe I am getting any spark knock or experiencing any detonation. I have never heard it in person, but has been described to me as marbles in a can and I definitely haven't heard that. I will check on the knock retard capabilities. I don't think my OBD Whiz logs KR but I think the Torque app on my phone does. I can log the drive home and verify that. Both programs can read standard OBDII PID's.

This is on my 2002 T/A and was tuned by Pat G. The 120*F IAT may be a little high off memory. I know if it has been idling in the driveway after a long trip home from work, it can reach 150*F. I can also verify that once up to speed and IIRC at WOT recently I was around 100*F IAT (laptop w/logs @ home).

The air supply is coming from the ram air and the previous owner cutout the bottom of the box so I am also getting air from under the front end that passes the oil cooler, condenser, and radiator.

If you can verify those abbreviations and explain the few I am unaware, I can attempt to get a log of everything.

joecar

VSS = vehicle speed
SPARKADV = ignition timing/advance on #1
LONGFT1/2 = LTFT = long term fuel trim (bank 1 and bank 2)

1SLwLS1

iTrader: (6)

Perfect, I've got those plus the rest setup to log. What about those last two?

joecar

If you have a fuel pressure problem, then it may be running lean which will cause misfires and/or lead to knock.

If your IAT is high, then the cylinder airmass will be low (since hot air has less density), this means:
- the air/fuel charge will be smaller (less power),
- the PCM uses more ignition advance which can lead to knock,
- combustion chamber temperatures may be higher (less fuel to cool the CC's) which can also lead to knock.

If the MAF is dirty it may report the wrong airflow which could lead to the wrong fueling.

If a plug is fouled, then that requires a "why?" question.

There are many things going on, so you have to log various things and try to correlate between them (based on known correlations)... it is a load of fun :^)

Knock is not always necessarily heard (usually it is, but not always).

If by checkvalve on the fuel pump you mean the pressure regulator, then that means your rail pressure is wrong so the injectors are spraying a different fuelmass than what the PCM thinks it commanded.

joecar

DYNAIR (grams/second) and DYNCYLAIR (grams/cylinder) may be called something else, and might only be available if the scantool has GM enhanced pids ability... they can be used to sanity check the MAF.

joecar

lol, thanks.

1SLwLS1

iTrader: (6)

I am thinking either too high IAT's or a failing pump. Either way, lean condition and detonation

As far as the pressure regulator goes, this is just what someone told me was wrong with theirs. I don't know 100% that this is my problem with multiple restarts. If the pressure regulator has failed and the cause of my multiple start situation, not detonation/misfire, the tune was performed with the pressure regulator being faulty so wouldn't that be ok?

Gotcha. I don't have access to these PID's.

I should be leaving work in about 30 minutes and will have logs up about an hour after that, maybe longer if it fails to work properly.

1SLwLS1

iTrader: (6)

Alright, neither of my programs can read knock retard nor the fuel trim in long term. I exported to an excel file but I cannot load it here.

joecar

pm sent.

joecar

In the raw log I see long term fuel trims banks 1/2 being zero always, this may indicate your tune is an open loop tune, can you confirm this...? If it's not, then then closed loop trimming is not working for some reason (bad O2 sensors?).

In the formatted log, when TP is 100%, I see the MAF spike down, there might be something wrong with the MAF.

Also, the sampling rate looks like 2 samples per second, which means alot of information is missing, so I can't tell if SPARKADV is dropped down due to knock retard... the software is not sampling at the fastest possible rate (10 samples/second, possibly faster with fewer pids).

Yes, your IAT is quite high, this does several things, this promotes knock and produces less power.

I'll be out of town next week, but I'll keep looking over your xls files to see if I see something else (it is harder to analyze a log via xls files, but it can be done).

1SLwLS1

iTrader: (6)

No, in my OBD Wiz, it has a dashboard which shows when it goes between open/closed loop, so possibly bad O2's, but I replaced them in October of 09. I wouldn't think they would go bad in 2 years, but maybe all that carbon and fuel has killed them?

As far as the MAF spike, I am 99.9% sure that its the data logging PID delay and the dip is when I am shifting.

I know I have the sampling set as fast as possible and only set to record those PIDs. It's a quality OBD reader too, not one of those junk $50 eBay units but I do agree the speed it very slow. I had a Chinese one and the speed was similar to this so I ponied up and spent $250+ for this Bluetooth/USB unit and something else must be causing the slowness.

Hey, I appreciate the help thus far and look at it when you can, no rush. I've got a few things to figure out too. If I can get the sampling up quicker, I will email it to you.

1SLwLS1

iTrader: (6)

Ok, here is a little update. Somehow, I had an "ah-ha" moment, similar to television shows like House. My moment brought me to my spark plugs and gap. I remember I used TR6 plugs with a 0.045" gap. That worked when it was cooler outside but this started happening with increased IATs as well as much higher ambient temperatures.

Now, I attempted to test this theory out last night but with a faulty headlight gear and the dark of night, I had to wait until this morning. This morning it seemed better, maybe not perfect, but better. The real test will be at lunch and on my drive home from work. That is when I can always get the malfunction to occur.

Here are pictures of my sparks plugs. Last night I replaced them all using the same TR6 plug and utilized a 0.035" gap. These are in order from cylinder 1-8 with (2) photos merged into 1 for each spark plug.

Cylinder 1



Cylinder 2



Cylinder 3



Cylinder 4



Cylinder 5



Cylinder 6



Cylinder 7



Cylinder 8





Now, after looking at the plugs, it seems that maybe the timing is too high for this particular setup? It seems that the color change, very hard to read BTW, is closer to the base ring than the electrode tip. Ideally, isn't it supposed to be in the middle around the bend of the ground strap?

What about the AFR? I cannot find any conclusive projections for what the porcelain is supposed to look like. I heard light brown with maybe a dark ring on top? I know its not supposed to be glazed or shiny.

The final thing would be the base ring with the heat range of the plug. I have read 1 full rotation is ideal. Does it appear as the TR6 is performing the job correctly or maybe one step colder in the Texas heat?

In another update, I went to the track this past weekend and none of the data I collected was worth while. Only (1) of (3) passes was successfully logged, the rest are garbage. I have that but the update time is soooo slow. It ran slower than last time which was 09/25/2010 when I let off before the end of 1/4 mile. Very disappointing on that note.

jimmyblue

iTrader: (11)

I don't see a mention of cylinder imbalance, these motors
seem to have trouble with #7 & #8 but any injector has
a chance of silting up the screen (end ones just do it
first as a rule). #7 looks different in the plug pics, than
the rest. Why?

Injector service might be a worthwhile investment if
you find no credible, global cause.

1SLwLS1

iTrader: (6)

I noticed that as well and unfortunately, the gap was not the issue.
O'Reilly Auto Parts was discontinuing 3M's 3 step fuel injector service kit a while back. They were regularly priced around $70-80 for the kit and I bought (2) for $30 each. Too good to pass up. I have an extra one laying around. I may perform that process tonight.

Some of the wires seemed to have difficulty clearly "snapping" onto the plug. So, I am going to pick up (2) Dorman plastic headlight gears and another set of MSD wires on the way home. Those MSD 'bendable" boots are nice for people with large primaries or some modification that requires the boot to escape contact with something, but it sure makes it a PITA to clearly snap them on to the plugs.

My co-worker who loves wrenching on hot rods with carburetors *cough* controlled fuel leaks *cough* swears this is an ignition problem. I kind of agree with him. I don't think it is a fuel issue anymore as it will skip in the higher RPMs but still pull to 6.5K so the fuel is there, maybe. To rule out high IATs I either have to move the oil cooler, bypass it altogether, wait until winter, or run WOT when the engine is cold - but I am not risking my valve springs to iron this out. I will update in the morning after I replace the wires, test it, clean the injectors and intake system, and test again.

transam19

iTrader: (1)

How do the coils look. Do any them have any slight cracks on them. Agree that it mite be ignition related.

1SLwLS1

iTrader: (6)

Well you and him were right, thus far. The coils look fine, I inspected them when I swapped wires. I replaced the headlight gear and then swapped the wires. These were the older style wires with straight boots for the spark plugs versus the kind of handle style boot like the newer ones. These were much easier to get a firm connection. I went for a test drive and it seemed much better but I still had a little hick-up around 5.5K holding through 6.5K. I went and grabbed some dinner and hit it again. This time and the consecutive 3 WOT pulls after, no misfire or hesitation. One or two of the old wires must of been damaged somehow. I am going to check resistance on them and see what I can find.

Now, this isn't a guarantee of success, as it wasn't super hot outside like it is on the way home and during lunch so I will update tomorrow with results after lunch. If everything holds true, I will head to the track on the 20th and save the 3M fuel service kit until that day so I can get optimal times!

LilJayV10

iTrader: (39)

What's up with #6?