Missfire under WOT ls3 swap PSi harness - Lateral-g Forums

cpd004 · #1 08-24-2015, 05:44 PM

I have an Ls3 from a 2011 Corvette and a 4L60e from a 4th gen f body rebuilt by RPM Transmissions. I'm using PSi harness #HAR-1038. Per their recommendation, I am using an E38 and T42 from a 2008 Chevy Express van 2wd 5.3.

I had Speed Inc do a mail order tune to get the car up and running. The car runs and idles fine albeit not the best shift points. They told me that it will need to be dynotuned to adjust shift points, among other things. I never felt comfortable driving the car far the way it shifted, so I had it towed to them.

The motor came from wrecked Corvette that had just under 12,000 on it. After having some misfiring issues, I decided to put new plug wires and plugs in it. The old wires had some minor breaks in them probably from the accident. There was glass all over the motor when I got it. Using a handheld scanner, the changes of the plugs and wires got rid of the misfiring. I didn't know there was a misfire under load until it went to the Speed Inc for tuning.

They changed the plugs once again, cleaned the injectors, double checked everything and have determined that it must be the harness.

The drivers side injectors lose power under load and WOT. I have even replaced the injector harness with a new one from GM.

PSi suggested my gold blade throttle body may be the cause and suggested I swap to an Ls2 style silver blade. They also suggested Speed Inc try lowering the WOT setting to 99% in the tune from 100%. This was an expensive trial that made no difference whatsoever.

I believe the only codes I have are for a range selector switch and something about the anti-lock brakes. I can post the specific codes tomorrow. I believe the range selector code is set to not illuminate the SES light.

Speed Inc suggested I pull the harness and send it back for testing. That isn't something I'm looking forward to.

I don't know what change a range selector switch will make or if it will even make any difference. I'm also not sure how to go about putting one in as it seems to be a part of the shifter in OEM applications.

I did find this link:
http://www.hptuners.com/forum/showth...-codes-problem

I would appreciate any thoughts anyone has on where to look and what to do. I can post the tune it has if that helps.

cpd004 · #2 08-27-2015, 08:58 PM

After calling PSi to see what steps they suggested I take before pulling the harness, Jeremy suggested I try a few things along with sending him the tune that I had. They felt that the tune was to blame and sent me one to try. That seemed to do the trick after a short ride. It finally felt like it had power! The harness was fine all along. Big thanks to Jeremy and the guys at PSi!

badazz81z28 · #3 08-27-2015, 10:23 PM

Glad to see you got it worked out, reading the initial post I felt it had to be the tune. Lesson learned here is who does your mail order tune. Some folks, I think Frost is one of them, they fix it it free it something doesn't work right for like a period of 30 days. Dyno tune is always best

Superlite Coupe · #4 09-09-2015, 09:25 PM

Quote:

Originally Posted by badazz81z28

Glad to see you got it worked out, reading the initial post I felt it had to be the tune. Lesson learned here is who does your mail order tune. Some folks, I think Frost is one of them, they fix it it free it something doesn't work right for like a period of 30 days. Dyno tune is always best

Gremlins that aren't really gremlins can be very frustrating (issues buried in the tune). Your tuner did the right thing - happy motoring.