Lby issues (03 with 05 top end)

[quinton]

I know this is a long shot without any knowledge on the truck but here it goes. Bought the truck needing a trans installed.
It’s a 2003 short block with all lly top end. All lly electronics is what it looks like and was told. Lly turbo, ecm, ficm, tcm, engine harness, and harness to fuse box. The truck is acting like the common lly issue with surge/lope only when warmed up, No codes. When being easy on the throttle it surges also. I have a log of it. Sounds perfect when cold then pretty bad rattle when warmed up. I’ve checked the Normal lly issues, wire harness rub, ice picked, fpr replaced. Stock tune and modified tune same thing. Throttle seems very touchy I low rpms/gears. I do know the fuel gauge reads backwards which I’ve read is tuning. Any ideas?

 

[2004LB7]

What the fuel pressure running at?

 

[quinton]

4350 psi at idle. Here is a log let me know if ya'll can open it.

 

[2004LB7]

if you have all LLY top end including harness, ECM, FCIM, etc and it doesn't idle right even on stock tune, then I would say you have a had parts issue.

in your log, the only thing I see that looked odd was the throttle didn't go below ~9 but I think there is a pid that does that and another that is correct. there may be others that see something in the log I dont.

 

[quinton]

Ya I was wondering about the throttle position one. I

 

[quinton]

So drove it a little more and any easy throttle it surges/ jumps. Set cruise down low around 50mph and it does it too. Any ideas?

 

[darkness]

Did you log any of it? I know nothing about anything but maybe fuel pressure is jumping around.

 

[quinton]

I just put another cp3 in today. There is a log in my earlier post that anyone wants to look at. That cp3 was weaker. But same issues with the lope when warm and constant surge while driving.

 

[Potthoffdmax]

I had a bad injector that would cause the same symptoms that you’re describing. Changed all 8 and cleared up. Balance rate also +15.. Not sure if this helps or not.

 

[dndj]

I took a look at the trace. You've probably already seen this, but I noticed at the beginning where the truck is idling, GM.MAINRATE (mm3) is bouncing around from 0 to about 5mm3. I'm no expert, but seems low? My LB7 idles around 18-20mm3.

 

[quinton]

I took a look at the trace. You've probably already seen this, but I noticed at the beginning where the truck is idling, GM.MAINRATE (mm3) is bouncing around from 0 to about 5mm3. I'm no expert, but seems low? My LB7 idles around 18-20mm3.

Yes I saw that, I think that log isn’t very accurate as I logged it again today and it was higher along with throttle position at 0% instead of 9% in park then took it for a drive and injector lifted. Previous owner did a bad helicoil job on it. Just got it fixed and will test again tomorrow.

 

[quinton]

bump. Still can not figure it out. Replaced engine wire harness, injectors, cp3. smooth as can be when cold and runs good but when up to temp lopes bad. The more you drive it down the road the worse it runs. played with the fass pump, bypassed it checked for leaks/sucking air. once you drive it for so long it starts injector rattle and throttle response acts weird. push the throttle its delayed then hits, let off and takes a min to respond. in low rpm it smokes bad until boost builds up. no codes. Any sensors that need to be changed with a lb7 block and lly top end? anyone see a FICM do this kind of stuff? I don't want to throw more parts at it and not fix it. Hard to find the problem when I didn't do the swap. Might just have to take this one to Josh! I believe its electrical now.