Hanging Idle?

This is driving me nuts! My '89 Mustang idles pretty good (B-303 cam) but the idle hangs at 1500 rpm whenever I let up on the gas. If the car it driven at slower speeds (like in stop and go traffic), the hanging idle problem causes the car to buck. I have to keep the rpms over 1500 or push in the clutch and coast if the engine is running below 1500 rpms.

The idle doesn't hang when I first start the car but once it's warmed up a bit, then the problem starts.

I've pretty much gone through all the standard idle fixes and even replaced the IAB. No vacuum leaks either.

At idle, it smells like it's runnning a bit rich but I just figured that's due to the B-303 cam. Other than the hanging idle problem, the engine runs strong and idles good.

Any Ideas?
Thanks,
Phil

I had a similar problem with my 88 GT I reset my computer and cleaned out and pinched the 2 ten point connectors located on the back of the intake manifold. I guess they weren't getting a good enough connection due to dirt and grime. Also TPS might be bad.

Hanging idle on EEC is usually a sign of bad or dirty 02 sensors...

The 10 pin connection is also a possibility, good call on that one. Ford had a TSB on that, they installed an extension harness to cure some problems with it..

check your tps voltage make sure its not above a volt..

Check your throttle return spring. Mine hangs on my truck all the time. The rpm it hangs at just depends on the rpm I turned it to. Got hung at 3000 last night so I ran it up to 5800 and bounced the rev limiter. It dropped back down to about 1800 then. Its just a work truck so if it blows it blows. I can fix it.