iac issue?

[01fordexpy]

Hey guys. I have a 01 expy with a 4.6. I have 2 problems with it. The first one I think is the iac. It idles fine in park, but while sitting at a stop in gear the rpms go down and the truck will shake but then the rpms come back up and it's fine for a 15 or 20 secs and then sometimes it does it again. This I'm assuming is the iac going bad. The 2nd problem is after sitting overnite and not letting it warm up as I start down the road it stumbles a little bit and then clears up, but once it gets up to normal operating temp it does not do this anymore. Could these 2 problems be related? Or is it 2 different problems? Thanks, Clint

 

[Maddog11]

Could be an IAC or TPS! On the stumble, I would lean more towards a misfire of somesort. Maybe coil, spark plug/boot and/or injector?!?

 

[ChuckD]

You can pull the IAC off and clean it with some PB Blaster and I would also clean the MAF.

 

[mikegigabyte]

Ive cleaned mine twice with low idle problems until I saw a vacuum line near the firewall rotted away helping to cause the idle to get low, once that was fixed and the last IAC cleaning everything went back to normal, maybe check the vacuum lines.

 

[Lane24]

I agree with mikegigabyte. Definatley check the vacuum line!!! Probably cracked or ripped at the elbow at the very back. You can tell by reaching way back in there and your finger will get sucked into the hole. Relace the elbow or the whole line, almost guaranteed to be the problem.