Semi-Rough Idle AFTER long drive

[FordGuy100]

After a long drive at freeway speeds (over an hour) my excursion has a rough idle. All fluids are fine, temperatures are fine, FICM was just rebuilt by Ed (with proper voltage). Everything appears to be fine, except after a long drive on the freeway.

Basically I will pull off, and the truck will return to an idle. The engine then starts to idle semi-rough. Not enough to catch on an iphone mic, but enough that I can feel it (and see water in water bottles vibrating) and so could my wife. Almost feels like its loping and or it cuts out for 1/1000 of a second every second or something like that. Its not burning coolant, smoking white, etc. On short drives, it does not do this, only after a long drive.

When I get back onto the throttle, its perfectly fine. Acceleration, power, fuel economy, all are fine. If I slow down and the rpm's drop from in gear rpm's (say 2000). Its not enough of a fluxuation to notice any difference on the factory tach.

First thing I'm going to do is to confirm all the wiring to the FICM is attached perfect, although I'm 99.99% sure it is. After that, thats where I need help.

After the last drive, it almost feels like it does it while driving as well. If I hold the throttle to where the rpm's are around 1200 in 1st gear (like 5mph) and I give it enough throttle to maintain rpm's but not enough to accelerate, it seems like it almost does it then as well.

Did a search and found this post:

"Hey guys,
My 04 6.0 F350 CC started having issues only after long highway run over 40 min or so. when i would get off the freeway and come to a stop the truck starts having a miss completely random miss that shakes the truck. sometimes happens 3 times every couple second sometimes more sometimes less. sometimes the miss is hard and really shakes the truck and sometimes small and barely feel it. No odd noises are made only a split second of no noise cause of the miss. This problem has slowly got worse to the point now of maybe only a few minutes running and it starts to happen lightly. Never dies. Starts everytime no prob and runs smooth till warm.

Took the truck to Mech. who charged me a few hundred to tell me i have no codes. "NO ****," right i new that. anyways they did the key on engine off and key on engine on thing and nothing. They cleaned my EGR and said they couldnt replicate the problem it was prob dirty EGR causing it. Drove it home and truck did it on the way home. Called the Owner and told him my feelings on the matter so we went for a ride. Hooked computer and dont you know it started doing it just like everytime i drive it. Must have been one lucky ride for it to not do it 1 time in 100+ drives.. anyways computer shows nothing out of the norm FICM at 48 ICP within norm. A slight drop in the 1,4,7 injectors around the same time the misses happen but nothing substantial and not really any lower than other cylandars. His guess says replace injectors but thats too expensive of a guess for me. Any body have issue like this and fixed it. Whats left that the computer wouldn't see.

He could not see fuel pressure with his computer. How can I check this?

Truck is not tuned has 102,000, Clean egr, Regular oil changes with filter, recent fuel filters <2000k. 15w40 rotella. Have guages turbo boost is 20 to 25 WOT, trans runs at 160, EGT below 800 most times jumps to 1100 WOT. Stock engine no delete or upgrades.

I have slowly noticed more lag off the line than normal with black smoke from pipe. Not much but more than normal.

Removed air intake pipes and spun turbo shaft spins super easy no play in it. I dont think the turbo could cause a miss though. Im no mech.

Any ideas or advice is greatly appreciated."

But nothing was ever found.





Its not super bad, but its bad enough that it makes me worried. Was driving down I-45 into Houston in traffic, and each time I stopped it started doing it. Makes you worried when your constantly having to stop with no real way to get off to the side of the road.

Thoughts or Ideas?

[RRSA]

Had the exact same symptoms, rough idle when warm after about 200 miles of highway driving. No codes no nothing, it started to do it randomly when cold after a few months. I replaced the IPR and it fixed the problem.