91 5.0 with erratic high idle

[1993SSP]

Got the car out for a drive today and cleaned it up. The idle is fine when it's first started, but during driving it wants to idle at 2K rpm, I have checked all my connections. What could be the culprit?

 

[Black1987Stang]

I vote for dirty/sticking idle air control valve aka iac but a few other examples could be...

vacuum leak
sticking throttle body or linkage...if the throttle plate is resting against the stop when its doing it then this isn't the prob.

I would unplug the iac when its doing it and see what it does then go from there...

 

[1993SSP]

the IAC was my first suspect, I'll check into it further when I have more time tommorrow, whenever it does it I can turn off the engine while driving and re start and the idle goes back to around 900rpm, just annoying as hell

 

[Black1987Stang]

I also heard a bad tps can do what you just described....check the output voltage of it at idle when it's doing it.....but my first bet would be the iac...

 

[1993SSP]

The voltage should be .095 right?? I pulled the IAC, It has been modded so that the valve is bypassed, the metal in the middle has been ground down. I'll prob go with the TPS, the idle would sometimes go back down when I would also tap the gas while in neutral.

 

[dcurtis]

I just recently had the same exact problem, not with the stang but, I thought it was the IAC but if I unplugged the tps my car would idle fine, plug it back in and the idle would climb to about 1900rpm's.

 

[1993SSP]

Looks like a new TPS for me, should I go OEM or pick one up from a parts store?

 

[asecretfile]

Got the car out for a drive today and cleaned it up. The idle is fine when it's first started, but during driving it wants to idle at 2K rpm, I have checked all my connections. What could be the culprit?

If it does ok at first startup but acts up afterwards might be your ECT sensor

 

[FrankenStang]

Hmmm, my Capri is doing the same thing.

*takes notes*

 

[Mr. Rustypwnz]

sounds like its idling too high and erradic?

 

[1993SSP]

The ECT, mounted in the coolant tubes that run to the heater core correct??

 

[dr59l]

go to ford and get a tps, parts store electronics are junk! i put three of them on my lightning till i broke down and bought a oem one. fixed it immediately

 

[asecretfile]

The ECT, mounted in the coolant tubes that run to the heater core correct??

yea