I'm having a cold idle problem with my truck. When I start it for the first time in the morning it starts right up and idles fine if not a little high at first. After a few seconds the idle gets rough and drops down to 500-600rpm. If I put the truck in gear the idle gets a little worse. The truck hasn't died on me yet, though. The thing is if I drive the truck a block or so all seems to be fine. It idles fine after a short drive....actually the problem is only at idle, once I get above idle everything is peachy. I only seem to have this problem when the weather is colder and the truck sits overnight. If I drive to work, then start the truck after it's been sitting for 4 or 5 hours it starts and idles fine.

To answer a few questions you may have:

Truck has about 60k on it.

I don't get a blinking SES light to indicate a misfire. I do have an SES light but it's because I haven't updated my tune after the headers and ORY I installed a little while back.

The plugs and wires are only a few months old and I've replaced both the fuel filter and pressure regulator. I've also cleaned my air filter, MAF and TB.

Maybe the fuel pump is the problem? I was thinking maybe the cold weather causes it to not pump enough fuel at idle? I'm open to suggestions here guys, I'm kind of out of ideas.

-Jake

 

Bueller?

 

sound like your fuel pressure may be bleeding off when it's not running, Mine does the same thing and I just installed my fuel pressure gauge so i'll post whatever I find.

 

Cool, I would appreciate that. I thought it was the fuel pressure as well (hence replacing the regulator). I just don't understand why cold weather seems to make it worse....thinking maybe my fuel pump is taking a dump and the weather exaserbates the problem.

 

Did you remove and clean the Idle Air Control valve when you cleaned the TB? I have idle problems every 40K or so and it is usually a very dirty IAC.

 

I had the same issue. I fixed it by adding 100rpm to the idle speed. Hadn't had the problem since. On a very cold start it'll rev to 900 but it goes down to 750 pretty quick.

 

I did not, but I will definately give that a shot. I didn't even think of the IAC.

 

I'm not sure if the "drive by wire" TBs have the IAC but if you do, it is mounted on the top driver side of the TB. Comes out with two screws. When I clean mine, I clean off the IAC and I shoot TB cleaner all around the hole it leaves when you remove.

 

My truck isn't DBW. I pulled the IAC off a little while ago and cleaned it up, I also shot TB cleaner in the hole the IAC goes in. Seems to idle better but the real test will be when I start it up tomorrow morning when it's cold. I'll update then.

 

Are you still running O2's with the new headers and ORY? If not that could be your problem.