my truck has a 4.2 with almost 58,000 miles, my truck sitting in park or at a drive through window afterr a few minutes it idles down really low and acts like it is going to die no problem when the truck is moving only stopped, also it did that once with the air conditioner running and i put it in reverse and it died, it started right back up though, so it is a little worse with the air running, anybody knoww what the deal is? Please help

 

A vacuum leek will cause that

 

And when the ac pump kicks in that puts alot of drag on the engine

 

im not a mechanic but when I was having idle problems I changed my idle air control valve and my truck idled fine after. Mine was so bad that it eventually wouldnt even idle when I turned the key unless I held my foot on the gas.

I talked to my uncle and he said that he was having idle problems and his port for the egr valve in the throttle body was clogged and said that he had clean that out and that fixed his idle problems. His symptoms seemed more like what you described.

other things I came across when trying to diagnosis my problem was fuel filter, vacuum leak, failing fuel pump, mass airflow sensor, possible miss fire problems (fuel injectors, spark plugs, COPs)

 

Run you codes and see if you are getting the IAC ones to set. If the codes are P1504 or similar, you've most likely have a bad IAC. It is funny, there have been 3 or 4 cases just this week of this very symptom. 2 have stated that was their problem. The other ones, I don't remember them responding back or if they did, they did something other than the correct procedure for checking, so they didn't know what their problem was still. lol

Anyways, without checking the codes to see what the computer is or has sensed in the past and present, it's like trying to pee up a rope. It doesn't work. Computer operated vehicles require test equipment to pinpoint the problem and correct it. You can, sometimes (rarely or even less), diagnose the problem, but usually you throw good money away, adding parts that MAY be bad, but usually aren't. Go by one of your local big auto parts stores and get them to read the codes if you don't have a reader. It will help you, and us, figure out what is wrong and how to fix it the cheapest, yet best way. Good Luck

 

Chase. Nice looking pictures of your truck. Looks very nice with the 20's on it, especially in the white.

 

Subscribed
I got the same prob with my '00 5.4l, and its throwing a system too lean code. Only does it on cool mornings though.

 

Trigger happy, I would check your intake gaskets for a leak. It's a somewhat common problem! Spray down the intake right after you start it up cold, when the problem occurs. Most likely the truck will start to sputter if there is a leak and you sprayed in that area!

 

Cool thanks TRD, I checked and one of the rubber fittings was loose. Haven't sprayed it down yet though.

 

Chase, any luck on your problem? I've been asking around about mine and the latest I've heard is my PCM may need reflashed. I was told the computer can't figure out when to set the choke, so it runs lean and gives me that funky idle.