The other day I replaced the ignition wires with Ford Motorsport 9 mm wires and the coil with an Accel Super Coil. Now the engine idles cold at about 1100 rpm in park(normal), but stays like that even after warm-up. Once it is actually driven, the idle is 1200 rpm in drive, and 2100 rpm in park.

I know its not a vacuum leak, because twice now, it has "cured" itself as fast it became a problem, then it "misbehaved" just as fast again.

When the MAP's vacuum line is disconected, the idel drops to a little below normal, but return any amount of vacuum, and the idle shoots right back up.

What's up???? Any ideas or experiences??
TPS??? MAP??? IAC???

Its a 1991 E-350 Class C RV, 460 Fuel Injected, E4OD.

Help!!! Thanx!!!!

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Max
'99.5 F-250 SD PSD CC Lariat, Transcommand, Chrome Turn Down, Fiberglass Lid, Heated Telescopic T-Tow Mirrors, Torreador Red, Stinger Kit. Built 2/99

 

The problem is likely to be in the IAC which is the idle air controller. It is located on the large metal air intake plenum and looks something like a metal toilet paper roll. Take the mechanical end of this apart and clean the carbon deposits off all internal parts and most likely this will cure a fast or surging idle

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2000 F-150, XLT, SC, 5.4, 4X4, 355 LS, ORP, Black/Silver, class III, single CD, sliding glass, med. gray, keyless, elect. shift, engine date 8-18-99, '93 Harley Fatboy Black & tons of chrome