intermittent rough idle

[beetlebz]

Sooo I went through the whole thing when I got my 94 xlt last week. aside from brake work, I removed the MAF and cleaned all the black crap off it, ran the tank almost dry and added a tank of high octane (91), added a can of seafoam to the gas tank, changed the oil, oil filter, checked the air filter, and new plugs and wires. The truck runs AWESOME! Until....

after running for a short while, whomping the gas will pop the CEL. shut the truck off and it goes away, until a while later, when you whomp the gas again. the plugs on the drivers side were all white... possible O2 sensor issue?

then im having rough running issues but its weird. If the truck has been sitting all night or for a long time, it will fire right up and run smooth. If you shut it off, and start it up again within an hour or two, about 40% of the time it will run rough, almost like its misfiring or skipping. not REALLY rough, but shutting the truck off and turning it back on will fix the issue instantly. any ideas?

 

[MrShorty]

Where the CEL came on, the first thing I'd do would be to pull codes from the computer.

 

[Russianblue]

my bet is the fuel pressure regulator. i wouldn't worry too much about the white on the plugs. any time you use an injector cleaner, seafoam etc, it'll discolor your plugs. techron makes them bright red in my old bmw's.

 

[BrooklynBay]

Did you ever replace the fuel filter?

 

[beetlebz]

picked one up today, as a matter of face. 10 bucks. i LOVE this thing lol parts can be so freakin cheap sometimes. Its going in tomorrow. 100 bucks for the fuel pressure regulator, though, so hopefully the fuel filter will do me some good, though im not so sure :\

 

[Four0Sport]

how did you clean the MAF? i had some k&n filter oil build up on mine and after cleaning it with MAF cleaner i still noticed it ran rough, it went out 2 days later. might also be the seafoam going through the motor. just some ideas.

 

[beetlebz]

cleaned the MAF with QD contact cleaner, actually. The thing that concerns me, or rather why im not so sure its a fuel problem, is that its so predictable and intermittent. It might not do it at all, but it if it does run rough at start up I just flick the key off and start the engine again and it runs fine. speaks to me about something electrical :\ sensor, perhaps.

 

[Four0Sport]

when my MAF went out the truck would start up and idle fine for a few mins and then the CEL would come on and the truck would miss. Driving it would run fine for a mile or so then start to surge and shift hard and i mean HARD. I took it on a lap down to the interstate and backtracked to my exit and when the CEL came on and it shifted I thought I had broken the sound barrier, it was that loud. Picked up a used MAF for $20 and everythings been fine since. QD electric cleaner is ok i guess but CRC makes a MAF specific cleaner that is different than the regular quick dry stuff.

- Jack