LLY running horribly

[Yellow Jacket]

I have a customer's c4500 and it had coolant coming out of injector bore cylinder #8. I tore it apart and replaced the left side head, after getting it back running it runs rough and has 2 codes for Accelerator Pedal Position p2138 & p2140, I checked the 3 voltages with a scan tool. APP 2 is low on voltage at rest position(3.8 v.) and at full throttle(1.8 v). I have 5 volts on the tan APP 2 ref wire, but didn't have a second person or lead extensions to ohm out from light blue wire from APP to connector J1 on ecm... if that wire is ok then it says to replace ecm... Which could be tied to the running like crap... it acts like it has a miss and balance rates go like this

Idle cold. Warm. Warm in Gear
#1:-3mm. -5. -7
#2:15mm. -.5. -7
#3:-.5mm. 1.8. 1-1.5
#4:-3mm. -3. -7
#5:-3mm. -5. -7
#6:15mm. 15. 15
#7:-3mm. -5. -7
#8:-3mm. -5. -7

#6 always stays +15, tried a good used inj same result
#2 is all over the range from 15 to -7, and is new
#1,4,5,7,& 8 start at -3mm and slowly get worse til warm to -7mm
#3 is all over too but more stable ranging from -2.5 to 3.5

I tried a different FICM, same results
Could this all be caused by the ECM?????

Anyone seen anything remotely like this????

Thanks in advance

 

[paint94979]

Time to check compression

 

[juddski88]

Or harness issue. But there's a lot of crazy little things that are possible

 

[dmaxbowtie]

The next thing I would check is compression. I just had this same experience a few months ago which ended up being low compression and turned into an engine build.

 

[Yellow Jacket]

I was leaning towards checking compression, but the pistons and bores were all in good shape when I had it torn down...

I'm leaning towards a harness problem (although no codes concerning it), especially since it didn't run this sh**ty when I brought it in the shop, unless I got F**ked on the head I bought "ready to assemble", but I don't think that could be it either...
I smelled and looked at the fuel too, nothing I can see or smell out of whack...

 

[b_r_a_d_79]

I know this is an old thread but im having some similar issues and was wondering what came out to be the problem on this truck.

 

[Yellow Jacket]

Compression check showed slight issues, tore enough off to remove upper valve covers and I had 2 cylinders that valves were tight on, I reran the overhead and it ran great...