Intermittent Rough Idle and Lack of Power

si3328 · Dec 19, 2015

This has been an on going issue for the past couple of months. This does not happen all the time though and is a real head scratcher for me. Truck starts up fine; cold, hot it really does not matter. It always starts fine. I will be driving down the road and get to a stop light and the truck as a really rough idle. At times I think it might die on me. When I take off it jerks and does not feel like it is going to go anywhere. It is not as noticeable at higher RPM though. You can still kind of hear the missfire sound. As I keep driving it clears it self up or If I stop and shut the truck off for about an hour and start it back up it runs fine again. This does not happen all the time, normally about once every other week or so. I have not be able to get a monitor on it while it is idling rough and running like crap because by the time I get back to my house to get it out the issue has stopped. I have a fuel pressure gauge in the truck and that holds steady at 60 psi and does not bounce around at all. The oil gets changed every 4k miles with Rotella T6 and RevX. I also change all the filters at that time too.

I check the DTC's regularly and consistently get the #7 contribution fault code. But, since it is so intermittent I do not think the injector is out. It feels more like a electrical issue. Maybe I am completely off though here and there really is something wrong with #7 injector.

Thanks for the help and let me know if you need more info and I will gather as I go.

6.0 Tech · Dec 19, 2015

Could be a mechanically sticking injector. Double check ficm voltage, then I would check fuel pressure, as it is the last one to get fuel. If that checks good, replace the injector and retesr.

si3328 · Dec 19, 2015

Thanks for the quick response. I will get under the hood and check FICM voltage with a multimeter tomorrow. The fuel pressure is right at 60-64 psi and does not bounce around like crazy like I thought it would when it is idling rough. So, leading towards replacing the injector now and not the wiring harness?

6.0 Tech · Dec 19, 2015

Yeah, a wiring issue will tend to set circuit codes.

si3328 · Dec 20, 2015

6.0 Tech said:
Yeah, a wiring issue will tend to set circuit codes.

Awesome! Thanks for the help. Will check ficm tomorrow and order in an injector to replace. I will report back if there are any more issues.

florida 6.0 · Dec 20, 2015

Mine had a similar issue years ago . Intermittent rough idle , take off . It was the ICP sensor harness worn out . You could wiggle the wires and make it run like crap .