Been working on a 2005 6.0 with 218kish miles on it. When I got the truck it had a contribution 2 code stored, no check engine light, just could see the code on the code reader.

Truck idled like crap, lacked power, so I replaced the injector. Truck improved but still had a miss, this time it had a stored code of injector 6.

Ordered another injector, got it installed today. Fired the truck up, ran perfectly, drove it around, absolutely 0 issues ran like a dream. Parked it for a few minutes before starting it again to wash it. Rough idle, not horrible, not noticeable. Cylinder 6 contribution code stored again, no check engine light.

So I drove it, I drove the hell out of it for about 15 minutes with the AC at full blast, WOT, etc etc. By the time I was done, truck was back to running smoothly.

Just walked outside after dinner to see if it would still perform well, or if it would idle poorly again, sure enough, 6 contribution, rough idle.

I just changed fuel filters with OEM, air filter is new. I just cleaned the EGR valve- although maybe it's not clean enough?? Oil change is tomorrow (had to wait for the filter to get shipped in).

Any thoughts ? I'm at a little bit of a loss on how to cure this miss, unless it's possibly an oil pressure issue from bad/old oil causing it?

 

Double dog sure you don't have some chaffing in the harness?

 

I don't notice anything visible, although I haven't torn the entire harness apart to look at individual wires or anything. I assume wiggling the harness will have an effect if it's chaffed at all.

 

FICM was covering for the bad injector, you swapped it so the next in line fell out, not terribly uncommon.

Where'd you get the injector?

 

The question I wonder is why even after replacement I still had an issue. Injector worked fine in the other truck and was a low mileage wreck from a friend who parts out trucks. I could move injectors and see if code follows- but seeing as though I've had it running perfectly since replacement, I'd be included to believe the injector itself is not at fault.

 

Yeah I follow, if it was a sketch reman I'd think it was the stick but if it's an original odds are less that it's the injector itself. What's FICM voltage doing when it's running poorly?

It would be odd for the same hole to be the only one going down due to a FICM or connector problem, but you can try to get under the FICM and check those connectors.

 

Just got back from a 20 mile test drive. Truck ran poorly from the moment I left, constant 6 contribution code, but the injector wasn't completely dead feeling. Came down my dirt road, hit a pretty big rut at about 40 and jarred things around, came to a stop at my gate. Truck ran smooth as butter, cleared code, drove around, turned off, restarted truck, code didn't return, still running smooth.

Judging by that, I'm thinking I have a loose wire or ficm connection, if a sudden jolt like that randomly makes it run perfectly again.

FICM Voltage while running around was 47.5-48. Once in a blue moon, it would dip to 47V on WOT up a hill, but never under, and never for more than a second.

 

I would recheck the ficm connectors. Ours is very finicky, took several attempts last time to get them seated properly. Then took a large zip tie and snugged it around the assembly to keep it snuck.

 

I was thinking as soon as it happened that I should duct tape the things in place... but zip ties sound much more efficient !

 

If one of the connectors is broken, don't do something drastic like cut the wiring off (happened here recently). You can buy replacement connectors and move the pins over for about $30 each. Riff Raff diesel sells each of the three connectors.

 

Drove truck again today. When I left this morning I did oil/filter, truck ran great. Drove into town about 10 miles, hit a speed bump, starts missing. Drive home, down the dirt driveway, bump, runs great again.

I tore everything apart checked the connectors at the FICM and the pins on the FICM itself and everything looks good and straight. The wires coming out of injector plug itself look fine as well as the plug.

It will occasionally stumble when its running smoothly just for a split second.

FICM Voltage always stays between 47.5-48, occasional dip to 47 for literally one second, but does not correspond with it running poorly/well.

I'm guessing I have a short or break in a wire somewhere in the harness itself, maybe I broke a wire inside while disconnecting from the ficm?? Does this sound the most probable?

 

The only thing that confuses me- I figured I should get an electrical related code if I had a wiring fault, not a contribution code... hmm

 

When our ficm was not connected properly, it only gave a contribution code. We previously has misfires on #2, so replaced all injectors on that side. Got done and then suddenly had #5 contribution code. Never saw that prior.
Reinserted plugs on ficm, got better, 3rd time was a charm. Runs fine now.