Cyc. 6 & 8 problems

[DIESELDUDE83]

I did head gaskets ,head studs, egr delete, oil cooler, new icp, new ipr new high pressure tubes,rebuilt heads and the sct3015 tuner. Truck runs great except at idle where she has a dead miss. scanner shows #7 contr, fail. and a few other codes. when I cut out each inj. my problem is with 6 & 8. Not 7. I switch 6 & 8 injs. with 2 & 4. And my problem is still with 6 & 8. My fuel psi is 65. FICM is 14v in and out & 49v. also my rpm is kinda all over. truck also has new crank and cam sensors. icp is good ipr good great psi everywhere. Could my PCM need to be replaced or flashed

[Tuscany]

Did you check to make sure that all the pins on the injector harness are fully extended and that the injector wiring loom isn't chaffed or worn through anywhere? Also make sure that the ficm harnesses are seated fully in the ficm.

[dannyboy950]

Since your injector swap did no good you may want to run a compression test on 6 &8 cylinders.

[southend]

If this is the first time running after the rebuild.......maybe bent pushrods?

Sent from my phone that somebody didn't help me get.

[DIESELDUDE83]

Ok thx sometimes it smooths out for a minute and idles great and do you know why the rpm gauge is all over and would bent pushrods allow the truck to run great at full thottle

[southend]

Originally Posted by DIESELDUDE83

Ok thx sometimes it smooths out for a minute and idles great and do you know why the rpm gauge is all over and would bent pushrods allow the truck to run great at full thottle

I doubt it if you say it runs great at full throttle, did you align the crank dowel to the 6 o clock position, before installing rocker boxes?

Sent from my phone that somebody didn't help me get.

[DIESELDUDE83]

not sure if the dowel was six or not. i did not install the heads or rocker boxes. my neighbor did. i just installed the motor. this is in a dump truck and this thing pins you back in the seat. i dont get it. and why would my rpm gauge be all over the place. do you know how to ohm out the injector harness any other ideas

[dannyboy950]

It may be a bad Tach or pickup sensor; wieing; loose plugin. Irratic feedback to the pcm can sometimes cause them to [hunt] constantly adjusting fuel strategy.

[DIESELDUDE83]

Thx dannyboy950. What would cause and irratic feedback to the pcm