increase in idle RPM

[snoplow]

I have a 1988 Thunderbird Sport with the 302 with SEFI. Has only 50,000 mi. on it. All of a sudden it picked up about 500 RPM at idle. I checked (visually) for obvious vacuum leaks and found none. I disconnected the throttle linkage and that didn't do it either. Any ideas? Which other components control the idle speed?
Thanks

[invoicee]

Originally Posted by snoplow

I have a 1988 Thunderbird Sport with the 302 with SEFI. Has only 50,000 mi. on it. All of a sudden it picked up about 500 RPM at idle. I checked (visually) for obvious vacuum leaks and found none. I disconnected the throttle linkage and that didn't do it either. Any ideas? Which other components control the idle speed?
Thanks

Does your engine have an idle air bypass valve? If so, it may be stuck in the open position. Try removing it and blocking up the holes it normally covers. Then see if engine runs at normal speed. If so, cheap solution is to get one from a wrecking yard, if available.

[snoplow]

Heck, I don't know, I'll do some searching to find out. I don't know what it would lok like or where it would be. My Haynes manual doesn't show one, but it's pretty vague. Thanks