GEN 5 Camaro goes lean after 5-10 minutes. Immediately fixed after re-flashing ECM.

[FL1A]

This is a gen 5 Camaro with a twin turbo setup. I can get the car to do everything right, but the fueling is wildly inconsistent. Seems that the longer I drive the car the leaner it will get. On a cold start I sometimes have to add 60% of fuel to get it to start and idle, then over the next the couple of flashes I have to pull all of that fuel back out.

Once I get the car drive-able and the AFR looking good, (especially after getting into boost a couple of times) the AFR will creep lean to the point that it will not idle and stumbles.

Here is the weird part, If I stop and reflash the PCM (with the exact same tune) it totally changes. It will then go back to however it was before, but alas, if I drive it some distance (5ish minutes), the AFR goes back lean only to be fixed by reflashing the exact same tune once again.

Car is in open loop and all the fuel cut, modifiers, etc. are turned off. Nothing should be acting on the fueling. I'd point towards something IAT, ECT, etc., but that wouldn't explain why it immediately goes back to right after I flash it with the same exact tune up. It also wouldn't explain that whatever tune up worked good the night before, requires such a massive amount of additional fuel just to get started the next morning.

One interesting note is the super low Cyl Airmass I am seeing, even with A LOT of boost I only make it down to about .60 g/cyl. I also Idle in the .08 g/cyl row.

Car is 430ci, has ID2000 injectors, twin turbos, 6speed, running on gasoline and has a ZR1 MAP.

I have tried running the car in MAF only, virtual VE, 2 bar SD O.S. and a blended model and it does it on all of them.

I have also tried running previous tunes from before the TT setup, tunes from other TT gen 5's that I have that work good, and a fresh file. All of them do the same thing. Car eventually runs like garbage from going lean.

I am going to attach one of many tunes I've tried in the car to no avail.

[10_SS]

Is yer Fuel Pressure rock solid? Reading exactly the same every time?

[FL1A]

Yes, it has a boost referenced 1:1 regulator.

[SultanHassanMasTuning]

log? are your O2's switching? active? looking at your fueling tables the data is not for ID2000

[FL1A]

log? are your O2's switching? active? looking at your fueling tables the data is not for ID2000

The injector data is most definitely for ID2000's. What are you seeing that makes you say that. This car has a vacuum/boost referenced regulator so you are not going to see the same scaled IFR like a normal static fuel pressure car.

[SultanHassanMasTuning]

whats your fuel pressure

[FL1A]

whats your fuel pressure

We've tried it at 58lbs and 43lbs, doesn't make any difference once the MAF is tuned.

[10_SS]

Sure sounds like the 02's are affecting fuel, but you say they are not... so.. post a log showing Fuel Pressure, airflow, MAP, IAT, with Injector pulse width (on identical runs), showing the different AFR. Your Pulse width alone should vary if ECU is messing with fuel (o2's, or other). Airflow/Map should vary if it's airflow, and finally and most obvious, fuel pressure should vary if that's your problem. Where's your WB02? Left, RIght, Both? Sure sounds like fuel pressure is changing... however... could be a wiring problem as you've had the engine out. CHeck grounds. I have read people changing ECU's fixing weird problems, but I think the datalog also reports correct data.. so the details are in the data.

[Mike@G-Force]

Funny how no one talks about the fact that e38 e67 cars after flashing will run richer than what its tuned for. I always Allow a car to idle for 10mins before doing any tuning.

[Bluecat]

I'm with you brother. I always see the same thing too. Not on cold starts, but any warm start after a reflash on e38 / e67 stuff. So I've always assumed it was tied to some estimated temp value that gets reset on a flash and causes some uncalled for enrichment. Bad part is I have never found any reason for it to be happening. Same command afr, g/cyl, even same logged injector pw. But a car that was running at 14.5 prior to a reflash fires back up on the same tune at 11.0 and stays fat at part throttle until she has been alive for 5 or 10 minutes. After that AFR's stay stable indefinitely until reflashed. Worst is when customer is present while on the dyno. Stock shit isn't a problem because they will idle happily while rich, usually smoother if anything. But if your dealing with a cammed car that is very picky about afr, damn things want to die and surge ass around. Makes you look like you don't know what your doing.

My thought has been this. Injector PW on GenIV stuff only shows the "fuel" component of the PW. We don't get to see what the actual pw is with offsets added in like we do on GenIII stuff. Only logical thing I can come up with is there is a table that adds or multiples the injector offset based of some calculated/estimated temperature value (like IVT or fuel rail temp thats is not physically measured) or a generic timer value. It's the only thing I can think of that would be adding fuel that wouldn't show up in the scanner. Also a unseen offset table would make sense on why the problem seems exaggerated to me on larger injector cars. Adding 0.1ms to the offset is a big deal on 160lb/hr injector lol.

Regaurless, to the OP, the solution to the problem is don't start to log or make changes based of any data you see until the car has been running a while. I always restart my scanner after the first 5 mile leg of my street drives to make sure its done with what ever its going to do. Then you'll have the opposite problem, rich at the beginning instead of lean at the end. It only seems to be relevant at part throttle, as at wot it never appears to be any richer right after a flash. So on the dyno I just deal with the nuisance until the wot pull starts.

[ZO6_Bryan]

I'm with you brother. I always see the same thing too. Not on cold starts, but any warm start after a reflash on e38 / e67 stuff. So I've always assumed it was tied to some estimated temp value that gets reset on a flash and causes some uncalled for enrichment. Bad part is I have never found any reason for it to be happening. Same command afr, g/cyl, even same logged injector pw. But a car that was running at 14.5 prior to a reflash fires back up on the same tune at 11.0 and stays fat at part throttle until she has been alive for 5 or 10 minutes. After that AFR's stay stable indefinitely until reflashed. Worst is when customer is present while on the dyno. Stock shit isn't a problem because they will idle happily while rich, usually smoother if anything. But if your dealing with a cammed car that is very picky about afr, damn things want to die and surge ass around. Makes you look like you don't know what your doing.

My thought has been this. Injector PW on GenIV stuff only shows the "fuel" component of the PW. We don't get to see what the actual pw is with offsets added in like we do on GenIII stuff. Only logical thing I can come up with is there is a table that adds or multiples the injector offset based of some calculated/estimated temperature value (like IVT or fuel rail temp thats is not physically measured) or a generic timer value. It's the only thing I can think of that would be adding fuel that wouldn't show up in the scanner. Also a unseen offset table would make sense on why the problem seems exaggerated to me on larger injector cars. Adding 0.1ms to the offset is a big deal on 160lb/hr injector lol.

Regaurless, to the OP, the solution to the problem is don't start to log or make changes based of any data you see until the car has been running a while. I always restart my scanner after the first 5 mile leg of my street drives to make sure its done with what ever its going to do. Then you'll have the opposite problem, rich at the beginning instead of lean at the end. It only seems to be relevant at part throttle, as at wot it never appears to be any richer right after a flash. So on the dyno I just deal with the nuisance until the wot pull starts.

I have a ZL1 with an E 67 PCM and I've been through this. You need to log fuel pressure and watch what it does right after a reflash. The fuel pressure gets ramped up to 60 PSI at Idle. And it takes a few minutes of driving before the fuel pressure control module starts to modulate fuel pressure properly. So the fuel trims go way negative and car runs rich until the fuel pressure stabilizes. I just throw away any data I collect for the first few minutes after reflash. Then start to log only once the fuel pressure comes down to the normal 50 psi at Idle and part throttle.

[SultanHassanMasTuning]

I have seen thing go as high as 70 psi at idle on cold starts on ZL1 CTS-v. but always the normal of 58 on the E38's

any car best to let it get up to temp reset fuel trims and start to tune. also look at your openloop (P/N)(GEAR) table as that is a multiplier

[LSxpwrdZ]

See it all the time after a flash... really makes it frustrating trying to dial stuff in especially at idle or light throttle where it seems to be affected the most, which I believe is some sort of pulse adder like Phil mentions. Letting one sit and idle for 10mins before you start tweaking on them really sucks but this is also why I try to tune the MAF and VVE at the same time to minimize my flashing and waiting.

[DSteck]

This vehicle in question doesn't use the FPCM anymore. It's not from that. Even so, that's not what causes the rich condition.



Log fuel trim cell. That's all I'm saying.

[Bluecat]

Don't beat around the bush. Turn loose on the education....

[MikeOD]

Funny how no one talks about the fact that e38 e67 cars after flashing will run richer than what its tuned for. I always Allow a car to idle for 10mins before doing any tuning.

I'm trying to figure it out too...I thought it might have been the fuel volatility thing, but I got HPT to add that, I turned it off and it didn't help anything.

[sssnake]

First off thanks for this "Funny how no one talks about the fact that e38 e67 cars after flashing will run richer than what its tuned for. I always Allow a car to idle for 10mins before doing any tuning."

I am a NEWB and therefore when things don't happen as expected I assume that I am making some kind of mistake. I have been chasing a rich to lean issue for a little over a week now. Given the statement above it might not be an issue.



"Log fuel trim cell. That's all I'm saying."

I do. I see differences in the AFR in the same FTC from log to log. Besides isn't the SD stuff disabled when in open loop MAF only? If so, wouldn't FTC be a non-issue?

Again I am just a newb but I have well over 40 hours into trying to find the issue. If it isn't really an issue I would love to know it.

[SultanHassanMasTuning]

^ go airflow>dynamic> high rpm and disable rpm changes to 300rpm/200rpm

now you will be in pure MAF mode

[sssnake]

High disable set to 2 and low re-enable set to 1 and I still the variances referenced.

[Pekka_Perkeles]

Funny how no one talks about the fact that e38 e67 cars after flashing will run richer than what its tuned for. I always Allow a car to idle for 10mins before doing any tuning.

Funny how this is not sticky in this forum.