04 mach 1 high idle issue

[kyle_1990]

I just this car from a friend of mine. It has a bbk 65mm TB bbk long tubes, o/r x pipe and a sct tuner. It had a high idle issue when I bought it I had a feeling it was the iac bad so I replaced it
Nothing at all so I read about the restrictor plate guys make to fix the issue so I made one. It fixed the high idle and ran great. But it started to hang at 1500 rpm recently. Once u snap the throttle it idles back down. so I figured maybe the TB was sticking so I took a look at it but its not sticking. I unplugged the tps and it idles nice and smooth with no hang. So I checked the voltage of the tps and it reads .96 at idle. Should I replace it? Or am I just wasting my time? I would really appreciate some advice to fix this annoying problem. Thanks!

 

[trinity_gt]

A high idle means too much air is bypassing the closed throttle plate. Either the IAC is acting up or the throttle plate is leaking in the closed position.

You might try unplugging the IAC harness and adjusting the throttle stop screw to get an idle of, say, 500RPM, then re-connecting the IAC again.

 

[wmburns]

What model YEAR car are we dealing with?

Note, if this is a 96-04 and unplugging the TPS causes the idle to drop to normal, that tells me that the PCM is not getting a reliable closed throttle signal from the TPS. If the problem were too much air, then disonnecting the TPS would not matter.

Don't get me wrong. I'm of the opinion that MOST high idle problems are the resuts of vacuum leaks SOMEWHERE.

Read the following post regarding how to trouble shoot high idle. Pay attention to how the TPS works to provide the closed throttle determination and why the value of the TPS no longer matters.

http://www.allfordmustangs.com/foru...-dieing-idle-idling-rough-14.html#post2260649

 

[twogts4us]

Good call Burns