my truck is doing the same thing. when it's cold does not want to idle. when she's warm it's fine.

i cleaned maf, replaced fuel filter, and air cleaner.

let's us know your findings.

 

could the rough idles be due to the idler air control valve? i herd somewhere that they can get stuck open or closed causing bad idle you can lubricate it with wd 40. just a thought and worth a try hope everything works out man

 

Well I got it back the next day---mechanic couldn't find anything wrong with it and didn't notice anything out of the ordinary. He cleaned the throttle body anyway and let me have it back at no charge.

It was a hot day, though, so the engine probably wasn't cold enough.




Took it back and it still did it in the mornings....though not as bad. This past Saturday, however, it had a really bad episode and the whole truck was shuddering between 1000 and 2000 rpms.

Called him back to get an estimate on how much it would be to replace all coils. Figured it was worth a shot....and if it didn't fix it then that was one less thing I'd have to worry about in the future anyway.




I didn't realize we had an IAC valve on the newer trucks since they are electronic throttle body?









When it had this latest bad episode the CEL popped back on. I had been under the assumption it was because of my aftermarket CATS (P0420 and P0430). If they aren't performing properly, though, could the O2 sensors be sending false information back to the engine, causing the A/F ratio to be off? Then once they (the CATS) warm up they somehow perform better?

Not sure if that has any reasoning to it at all, but I've been getting those two codes (throwing the CEL) more and more frequently.

 

im not sure about the newer trucks but my 01 has IAC valve.

 

04+ does not have an IAC.

 

I was under the impresion that we (04 and up) do have an IAC and that it is part of the throttle body, not a speperate part.

Correct me if I'm wrong.

 

an IAC is a valve that bypasses the throttle plate for idle speed. With the 04+ they use a servo motor to control the throttle plate so their is no separate IAC. I guess you could say it is built into the function of the throttle body.

 

Just as an update, I replaced my COPs this morning. So far it seems like it's idling better, but I'll see how it does over the next few days. Hopefully this fixed it......and now I just have to worry about buying new cats.

 

 

Final update (I hope). Were a few misfires in the first 20 minutes or so after switching out the old coils (Saturday morning). Since then....nothing. Rides like a dream again.


Didn't notice anything severe about the old coils....nothing stood out. There were only two things. The little tabs at the coil-end of the spring were slightly corroded. Might have been just enough to cause problems. Also noticed that there was no di-electric grease on the inside of the boots in the old ones. They were bone dry. No idea if either of those were the problem....but it seems to be fixed.

 

Hope it stays that way Matt