The idle on the engine of my 93 RX-7 jumps between 1200-1500rpm while the stick is in neutral. If I press the clutch and put the stick in gear, whith the clutch still pressed, the idle jump gets much worse. Has anyone run into this before? Any ideas on fixing the problem?

 

You could have a bad vacuum leak or the car needs tuning. You can try unplugging the ISC(idle speed control) and see if that clears things up. Really you have not given enough info to make any educated diagnosis.

 

Idle problems are usually one or a combination of few things.. the most common being a vacuum leak, or improper tune.

I'd go the vac leak route as bonzai BlueTII said - make sure a hose didn't pop off. Easy way to do this is take a vacuum line off the manifold and see if the idle changes. If it doesn't, you probably have a leak somewhere else and the new leak isn't affecting it since it's already pulling air in elsewhere.

The Idle speed controller is on the back side of the upper intake manifold. It's a small cylinder shaped device with a electrical connection. I'd give that a shot too.

 

The vacuum leak theory is only applicable if he is running a PFC or other "Aftermarket" ECU. The stock ecu compensates for vacuum leaks.

Stock ECU: Could be a faulty ISC, TPS adjustment, Dashpot adjustment, etc.

Aftermarket ECU: could be all of the above, plus a vacuum leak and then some.

There have been mulitple threads that discuss this topic. Try searching the forum and reading all of the info you can on this topic before messing with the idle.

Joe

 

I don't have an Aftermarket ECU and I had a vacuum leak when my intake manifold gasket blew. it also idled from 1200 to 1600ish rpm. replaced it and the car was fine.