Vehicle revving itself intermittently.

Ok guys. I have an 87 turbo coupe that was converted to 5.0 t5 along time ago. I've daily driven this for over a year and recently something strange started happening. Every now and then the engine will rev itself. Sometimes while I'm sitting at a light bam it will just shoot up to 2500 and stay there. I Cleaned the iac and no change. I set the tps no change. I replaced the tps no change. I didn't change anything and it isn't a vac leak. When it's happening if I turn off the engine and remove the key and restart it will go back to normal. I'm stumped. Any suggestions?

Also it hangs revs now when coming to a stop.

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Originally Posted by steelhorse92

I Cleaned the iac and no change. I set the tps no change. I replaced the tps no change. I didn't change anything and it isn't a vac leak.

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What did the IAC look like prior to cleaning? Was it in need of cleaning?

what are the counts for block learn multiplier showing? If this data is showing within range, or is being commanded to change it could be a few things. ECM, another sensor going haywire [EGR] or an overlooked vacuum leak.

Not very dirty at all.

How does the car run with the IAC disconnected?

It doesn't run with it unplugged.

I've learned just because the iac is clean doesn't mean it's functioning correctly, they are cheap go get a new one

Is there any way for you to data-log the car [tweecer] ?