LQ4 swap surges and goes into and stays in Open loop/Accel on tip-in

[DC12VOLT]

I am tuning and troubleshooting a stock LQ4, P59 ECU, and TAC module out of a 2003 Envoy swapped into a square body pickup with a TH350. The customer used an ebay Gen3 LS swap harness, which I had to repin in a bunch of spots to get it running. I disabled transmission control and all codes that don't apply anymore that I can think of. It starts and idles fine now, but when load is applied, in gear or in neutral, the ECU goes into open loop and it will surge until you get out of the throttle, but stay in open loop. A key cycle will get it to go back into closed loop. The throttle plate stays open when this "rev limit" is happening, and fuel pressure remains stable. The only trouble code that sometimes comes up is a P0327 knock sensor circuit 1, and I suspect a bad knock sensor as it produces 45mV at idle and continuity to the ECU is good.

I've attached the calibration, VCM suite information, and three logs.

Thanks in advance!

[twenglish1]

It almost looks like misfiring really bad, on multiple cylinders when underload, O2s flatline nearly the entire time its surging. Now the question is, is it leaning out and causing misfires, or is it showing lean because its missing? Fuel pressure would be easiest to rule out first.

[NERDBIRD]

Fuel pressure is good running about 58 never dropping

[twenglish1]

Since it appears to be affecting both banks equally, fuel pressure is good, not seeing any knock retard, throttle position holds steady, wondering if there is an issue with the crank signal? Wiring issue, faulty sensor, etc.

[NERDBIRD]

Since it appears to be affecting both banks equally, fuel pressure is good, not seeing any knock retard, throttle position holds steady, wondering if there is an issue with the crank signal? Wiring issue, faulty sensor, etc.

Yes we have checked the crank sensor wiring to ECU and replaced the sensor. Still has the same issue.

[ns158sl]

How many DTCs have you turned off?

[Alvin]

This sounds like BTM. Often on swaps the guys won't hook up the brake signal which needs 12v while off the brake. It's OK to leave this disconnected if you have a non electronic trans but you have to then disable BTM. I did this for you here.


TanSquarebodyCal3 - Alvin.hpt

If this doesn't get it attach your 100% bone stock file out of this.

[DC12VOLT]

I tried Alvin's tune with BTM disabled and got the same result. I've attached the original calibration and the most recent log. Fuel pressure really does appear rock solid.

It acts like a slow-hysteresis fuel cut rev limiter. I checked spark and it has good spark the whole time it's doing it. I'll check for actual injector pulse after grabbing a noid light.

[ns158sl]

Well the first stall the MAF(along with the internal IAT) didn't come online. After the restart it came back. Is the catalyst test disabled?

[NERDBIRD]

This sounds like BTM. Often on swaps the guys won't hook up the brake signal which needs 12v while off the brake. It's OK to leave this disconnected if you have a non electronic trans but you have to then disable BTM. I did this for you here.


TanSquarebodyCal3 - Alvin.hpt

If this doesn't get it attach your 100% bone stock file out of this.

[Alvin]

It doesn't look tuning related to me. Fuel pressure or some other wiring issue. The o2's are dead lean while this is happening even with a huge injector PW.

[threetoes]

Howdy y'all,

I found the source of the mystery limiter, was coming from our friend "Abuse Mode" - Sounds to me like abuse mode would be the OPPOSITE of a limiter, but I guess not.

So if you find yourself with a mystery crappy launch control, look for those tables under torque management.


Cheers!

[blindsquirrel]

Is this multiple people working on the same truck, or the same person using three different usernames?

[NERDBIRD]

Just 3 guys trying to figure this out