Sudden Lean Condition When MAF Tuning E38 PCM

[ryanater]

I just finished an LS7 swap in my 69 Camaro and I?m having issues with the car going way lean when tuning using the MAF. The engine has a custom 249/258 cam, ported heads, 11.5:1 compression, FAST intake, and a 102mm TB. I'm using an E38 PCM and a modified engine harness from a 2015 Z28. I was able to tune my previous LS1 with the Gen 3 0411 PCM, but that's the only experience I have.

First of all, I've dialed in virtual volumetric efficiency tables reasonably well below 4000 RPM. The only issue I ran into is the engine wants to pull the throttle above 4,500-5,500 RPM when near/at WOT even though I thought I turned torque management off. It also seems like the cutoff RPM is dependent on what gear I'm in.

Now that I've switched over to MAF tuning, I'm running into two problems that won't allow me to dial in the MAF frequency tables.

1. The engine still wants to limit itself around 5,500RPM when at WOT. I'm guessing it's a simple parameter I missed somewhere.

2. The big problem is that the engine will randomly start running lean. You can see in the posted log, that about half way through the drive it starts "snapping" lean on me for no apparent reason. As the drive goes on, it gets more frequent until it's almost always in the lean condition. There is no obvious cause since RPMs, MAP, MAF, Spark, Fuel Pressure, Injector DC all seem to stay the same when it does it. This isn't a wideband issue because the car will barely run and start popping really bad when it does this. I did find that if I brought the RPMs up and gave it some throttle it would typically go back to a normal AFR momentarily.

Things to Note:

I am running LSA/LS9 injectors that were bought used. I'm almost wondering if they were modified because the VVE table I ended up with is SO far off from the stock table. So possibly incorrect injector data.

I took the plugs out after the drive to see if it was maybe isolated to a single bank or cylinder, but all of the plugs looked similar to each other.

It's odd that the injector duty cycle isn't changing when it goes lean, so I still haven't ruled out a harness issue.

I tried turning off the knock retard to see if that could be the issue ? it wasn't

Probably has nothing to do with it, but the transmission is out of a 2002 Camaro, so the gear ratios are different.

[ryanater]

I can't upload the log since it's too large, but it's sort of doing it in the smaller log I could post. I will see if I can get something better tonight.

*I was able to modify and trim the log to make it upload*

[ZincGT]

your o2 sensors are not reading. Do you have a wideband? if you are open loop tuning your tune is not setup to do so. If you are adjusting the tune based off of STFT/LTFT you are getting incorrect information from your o2's.

[ryanater]

I do have a wideband with the O2 sensors disconnected.

[ZincGT]

plug your o2 sensors back in and see if it changes, post up your log after

[castorjames]

...

[ryanater]

plug your o2 sensors back in and see if it changes, post up your log after

Would it be better to properly put the PCM in open loop?

[ryanater]

The correct log is now uploaded showing the random lean condition.

[ZincGT]

Would it be better to properly put the PCM in open loop?

yes

[ryanater]

Well not my proudest moment, but I found that it was a loose connection on the bank 1 coil ground. Sorry for the pointless thread.

However, I'm still trying to figure out why I'm limited to 4,000 RPM in 1st gear and 5,000 RPM in 2nd and 3rd. (Haven't hit the rev limiter in 4th+ yet)

[pannetron]

Check your Fuel->Cutoff,DFCO->In-Gear table. There's a RPM limit for each gear.