stuttering/rough idle - frustrated

[philhyde]

My 2006 6.0L w/78K miles has lately been plagued with an intermittent rough idle situation. The problems I am experiencing are rough idle, stuttering off-idle, very limited power and extended upshifts.

I can't seem to put my finger on the triggers, but I would swear it was temperature related. I know it sounds silly, but it's really the only thing that has changed. Overnight temps were in the 60's last week, and that's when I started having problems.

I seemed to notice the problem after driving short distances, stopping and then starting again, before the engine fully warmed up.

After more "intense" driving (highway) the problem seems to go away.

One other thing I should mention - the last tank of fuel was 100% biodiesel. The idling problem seemed to be the absolute worst when I was very low on fuel (Saturday). In fact, the low fuel light was on. I filled the tank up (diesel), and still had the idling issue. After a quick bolt down the highway, no more rough running.

Now, I'm no stranger to fueling issues with biodiesel. If my problem weren't so intermittent, I would suspect fuel filters. However, they were both replaced at the beginning on this month.

Over the weekend, temps warmed up (90's yesterday), and this morning, I did not notice anything except a slight rough idle.

I was planning to get the truck into the shop today, but I held off because I didn't want to waste time with a "cannot reproduce" situation.

History: this truck received a new turbo last month. I towed a 4000lb trailer about 3000 miles earlier this month. Performed flawlessly, but toward the end of the trip, I noticed a faint coolant smell. I have since replaced the coolant reservoir cap and haven't really noticed it. Coolant level is at MIN, and I have not tried to find traces of dried coolant anywhere.

Also, I have been running custom SCT tunes from Innovative Diesel. I was running the street tune, which I removed on Friday. This did not seem to make a difference, nor did applying the tune (weeks ago) coincide with the problems appearing.

Thanks in advance for any tips.

[chuckles]

can you monitor sensors/pids??

[dieseldan2005]

It sounds like a dirty egr valve.

[philhyde]

Well today the dealer replaced the FICM. Some final testing tomorrow, but it appears to have done the trick.

The symptoms they troubleshot on the scanner or computer (or whatever they used) were dropping of #1 and #2 cylinders. They were thinking bad injectors, but then the engine started misfiring on other cyls.

[dieseldan2005]

I forgot about the FICM. Hopefully that did the trick for ya.

[philhyde]

Plot thickens today. After FICM replacement, still showing 2 bad injectors. So they are replacing those.

What concerns me is that yesterday the tests were showing other injectors were bad as well.

I'm not feeling as confident about the repairs, but what can I do. Time will tell, I suppose.

[philhyde]

More news...

After replacing #1 and #2 injector and FICM, engine is dropping an injector on the other side of the engine. Will have to wait until next week for the repairs. At least it's all under warranty, but I'm kinda wondering why the injectors are all failing.

[dieseldan2005]

That is weird. I have heard of a couple of guys that have had the same issues, but its not that common. I wonder if they can tell when they pull them what happened to them.

[STORMTROOPIN]

just a thought but take a good luck over your wiring harness and those stubborn *** conectors on the ficm. Check to make sure that theres no corrosion or bent pins.

[philhyde]

Wouldn't the dealer scanner/computer be reading low pressure, if the condition existed?