Engine/Transmission (1998.5 - 2002) brake pedal soothes ROUGH idle

[pdxkevinc]

My 98. 5 24v has had a rough idle since approx 52,000 miles. I'm at 76,000 now.



It is rough, only when hot



When I say rough, it is an intermittent missing sort of feel. sort of bump... . bump. bump... ..... bump. bump. bump... .



Stats: new lift pump,VP44,valves set, and oil analysis by Cummins. I've paid a lot of money to deal with this stupid anoying problem.



Anyway, it has really been giving fits lately. I have about 10 minutes of rough idle last night so I sat and played with it a bit. I had the park break on, manual in neuteral, everything powered off that was electric. I found that if I mashed the brake on the idle immediately straightened out... a purr... took my foot off the brake and bump..... bump. bump... etc ... I walked through this same scenario this AM in the parking lot at work... consistent ...



Any ideas on what the heck pushing in the brake pedal would do for a rough idle?

 

[ROADWARRIOR]

Mine has done this when up to temp. the last three winters. Only does it when it is roughly 40 or colder. The lower the mercury drops, the rougher it idles. On a snowmobile trip last year, it was roughly 10 below when we got there and it idled so rough, it was shaking the crap out of the cab. The chevy guy with me just kinda looked at me and asked if we we're gonna get to the motel? Mine clears up above 1200 rpm.



Dan

 

[Ncostello]

Same problem here. Just as you described. I never noticed the brake pedal remedy... mines always been turning on the air conditioner which also loads the engine.



I am however not happy to hear a new VP44 didn't solve the problem. I bought a used one w/ 10,000 miles on it hoping that if I installed it my rough idle would stop.



It was really making me mad last night. I hauled new big screen TV for a friend. When I arrived and backed up to the house... the truck was sitting there purring away at idle... with the bump bump bump in the idle about every 5 seconds. The guys wife asked me why it did that. Needless to say I was embarrased.



I installed RV275's hoping they (being new) would perhaps clear it up. Didn't happen. I've tried many things short of installing the VP. When I install the VP I'm also putting in some new injector fuel tubes in the head. Trying to eliminate all possible sources.



My biggest problem with this is that even though its noticable at idle and not under load... it still occurs under load. I have confirmed this by running the engine via INSIGHT at cummins. It shows various injectors are only running at 60% at different times. Its a "rolling" problem in the injection system.



You just dont really notice it when the engines loaded up.

 

[JFinke]

My 01 HO will do it about every 30 seconds even after it warms up. It just goes bump..... bump and then normal again. If it 's at a stop sign I can make it do it again by letting out the clutch in neutral and loading the motor a little by having to spin the trans up to speed. Any time someone asks me why it's doing "that" I just tell them it has a lopey cam installed. Normal response is "oh, cool" If I want it to sound normal while I am sitting somewhere I just turn on the exhaust brake. Never does it under the slight load.

 

[pdxkevinc]

Thanks for the feedback, guys.



Ncostello, I am very upset to hear that this is occurs under load. I presumed that it wasn't... . I've spent so much money on this problem I could puke...



I don't know who should be more ashamed, Cummins or DC ! Of course all my ford buddies know about this crap and it didn't help that after cummins put a new VP44+lift pump to no avail, I popped 5th gear about 500 miles later... money trap. .



If you ever smooth yous out, please please let me know how you did it.