EFI warms up and then fast idles?

[markesmith]

I have a 5.o Ford Racing Crate motor, 340HP with Cobra EFI intake. Motor starts quickly and settles to an idle of 850 +/-rpm's upon reaching operating temperature it races up to 1,500 - 2,000rpm's. Any quick thoughts on what the issue might be????

Thanks,

Mark

[Boydster]

The computer is using the idle air solenoid to control idle... wont take much of an offseat to raise it that high. Sticking or stuck? You can take em apart and clean em up.

[markesmith]

Thanks for the response Boydster, do you think this could be caused by lack of use? At times, and I hate to admit this, my car has sat for a few weeks at a time without use!

[Boydster]

Could be, hard to say. It's just an aluminum housing with a metal piston that moves in & out, controlled by the computer and controlling the amount of air that bypasses the throttle body. It's mounted on the side of the throttle body. The breather line from the valve cover comes into the throttle body just before this, so it tends to get a bit gummed up. If not used for a while, that gum could become sticky and hard and prevent it from working correctly.

It's pretty easy to remove, just 2ea 10mm bolts. Be careful with the gasket underneath. If yours is the type that can be taken apart, there's 2 screws to remove the electrical from the mechanical sections, then you clean it all up.

There's a whole Surging Idle checklist over on Stangnet that addresses this sort of problem on the 5.0. But this is the most common issue and easy to try before moving on to the other items.

[markesmith]

Thanks Boydster, been a while since I have been on the build sites. Were invaluable during my build, cant thank everyone enough for the help!