Lsx engine problem....misfire???

[First c10]

Hey guys today I went with my son out of town and after he got on it to pass a car the engine sounded like it was or had a misfire. It was sporatic. It's would like skip a cylinder or cough like an old small block. He said that it would do it only if he got on it. Hot rodding it. I had him pull over and shut it off. Restart it and it ran fine until he got on it again.
Does anyone know what it is or what I need to check?

2011 5.3L LC9-6L80E is the motor package.
Thanks Scott

[BR3W CITY]

First things first scan the codes and see what pops up. Generally if there was a misfire, the CEL would flip on, if it was a repeated multiple misfire it would blink (usually)..but swap vehicles don't always behave that way.

Either way, the ecm would have a code present for misfire, and tell you on which side/cylinder it occured. More than 1 will be present if it happens at various times.

The feel of a misfire doesn't always mean a misfire tho. Since it only happens at Wot/high throttle, its a repeatable problem. I'd also consider taking a look at the fuel filters, make sure there aren't any restrictions in the fuel system, and that your maintaining fuel pressure. You might need to toss an FP gauge on the rail and see if high load/high rpm is resulting in a drop in FP.

Let us know what codes it has, we'll go from there.

[First c10]

Ok I will check that. The misfire feel is when we are just driving normal. Not during a wot event. The misfire is after you jump on the throttle and than get back to normal driving. Just wanted to make sure I was clear on when it does it.

[First c10]

Ok so no CEL. The only code that pops up is p2534 "ignition switch run/start position circuit low". I am not sure what that is.

[aknovaman]

Clean your dirty sticking injectors.

[homemade87]

Originally Posted by aknovaman

Clean your dirty sticking injectors.

I agree with this . It is the most common problem with swap engines that sit around a while . Ls injectors are bad to stick if not used for a while.

You can make a homemade injector cleaner with a syringe and flow them both directions to get them clean . I made one for my swaps. Worked pretty good . Look on youtube you will see how there made .

[First c10]

Makes sense! I was thinking my wiring for some reason. I will clean them and let you know
Thanks for the help.

[Hart_Rod]

Originally Posted by First c10

Ok so no CEL. The only code that pops up is p2534 "ignition switch run/start position circuit low". I am not sure what that is.

FYI, the 2534 code is a TCM code that you won't be able to clear unless you have someone with a Tech II.

[homemade87]

Here may be a solution for your p2534 code for the 6l80e.

https://forum.efilive.com/showthread...n-engine-swaps

Heres some info on ls1tech . http://ls1tech.com/forums/conversion...dtc-p2534.html

These were a couple I found with a quick search . I am sure there is many other sites that have info on this .

[First c10]

Well guys thank you very much I think I might have fixed both problems I have the same problem in third gear and didn't realize it was limp mode. I will try and rewire the TCM power with a relay through the ECM. And will clean the injectors and see if that fixes both my problems.
Now if I can get the torque converter lock unlock correct it would be great
Thanks again Scott

[Hart_Rod]

Originally Posted by First c10

Well guys thank you very much I think I might have fixed both problems I have the same problem in third gear and didn't realize it was limp mode. I will try and rewire the TCM power with a relay through the ECM. And will clean the injectors and see if that fixes both my problems.
Now if I can get the torque converter lock unlock correct it would be great
Thanks again Scott

The A6 TCC receives a signal opposite of the A4s.

[First c10]

Yes it has to have power when brakes applied and ground through the light bulb when brake pedal not applied. (I think). I waited it that way but it's not working.
Rob did you ever find the place in HPTwhere you can see the lock/unlock of the TC?

[Hart_Rod]

Originally Posted by First c10

Yes it has to have power when brakes applied as ground through the light bulb when brake pedal not applied. (I think). I waited it that way but it's not working.
Rob did you ever find the place in HPTwhere you can see the lock/unlock of the TC?

You have to log TCC pressure I think, I would need to look in one of my tune to give you the correct PID (shoot me a PM later). It's not as simple as on/off in the A4's. When the pressure is zero it is off, but the tune controls the pressures based on a lot of variables. You can set max and min pressures, but the computer will vary it based on different parameters in the tune.

[First c10]

Rob, I think you may have a tune of mine from Super 73(Shawn) last year.

[First c10]

I am wiring up the 4.8/4L60 and am going to wire in the #59 wire to a relay for the TCM because it is much easier to do now. I will be doing it to the 5.3/6L80 soon and will be cleaning the injectors (both engines)as soon as the rest of my cleaning supplies arrive...

[First c10]

Ok so I drove my sons truck this weekend and can't stand the 3rd gear shifting.... Limp mode or not I ordered hptuners. So pocket is lighter and going to get my feet wet. I will need assistance guys. Hope I can figure this out.