Intermittent rough idle and CEL

[delta265]

I have a 99 3.4 all stock except for a K&N intake system, exhaust, and 180k miles. Sometimes it fires right up no problem, other times it idles super rough (like a cammed V8), the whole rig shakes, and recently threw a CEL. It feels like one of the vacuum lines came off, but I checked all those, and cleaned the MAF. Problem still persists....

Any ideas? Maybe a bad plug?

I'm going to try and borrow a code reader tomorrow.

 

[Whitson Metalworks]

my wifes idles roughly sometimes, i suspect a coil going out. not sure how you could check yours though without a timing light or something. hopefully the ecm caught it and will let you know.

 

[delta265]

So yesterday the truck started running fine again, and today the CEL went away completely...figure that one out. Bad gas maybe?

 

[trdrun]

Possibly dirty Idle Air Control (IAC) valve? Right below the TB, it can be taken off and cleaned.

 

[hairysrunner]

I 2nd that on the idle air control valve. I just put a new one on this past weekend. i had the same symptoms you had. When I took the old one off it was crammed full of crap that looked like wood. Seriously. it was coolant that had accumulated inside. now my runner starts like a dream and runs great. i got my mine at Advanced Auto Parts for $202.00. it did not come with the very important gasket, but Advance has a gasket kit that contains the needed gasket for the IACV. they took it out of the kit and gave it to me.

 

[delta265]

So it happened again today, I decided to take it to a local mechanic who said one of the injectors is not working. He quoted me 500 bucks in parts and labor, I guess the intake plenum has to come off...Does that sound legit to you guys? He also said that its rule of thumb to replace all 6 since at the same time, but I nixed that.

I'm comfortable doing basic stuff to my rig, but never attempted anything like that.

Thoughts, opinions?