I have a little rough idle. I thought it was the TPS but when I unplugged it the engine set off the engine light and all kinds of things happened so I figured it was good because it stopped when I plugged it back in. I noticed though when I unplugged the IAC the car does nothing does anybody elses do this or is it normal

 

You can test the TPS sensor with a multimeter. It will have a ground wire, a +5V reference wire, and the sensor return. The sensor return should read ~0.5V at closed throttle and ~4.5V at wide open throttle.

As far as whether there should be any change when disconnecting the IAC valve, it makes sense that there wouldn't be. The only time that the IAC valve really moves on a warmed up vehicle is at idle when the a/c kicks on and off. It will gradually move in as the vehicle warms up.

 

so no change huh? Come to think of it my car ran pretty smooth with A/C on but now that it's cold outside the A/c is off and it runs like crap even though what your saying it should probably be the opposite.. The only other thing I can think of is my Spider has a tiny leak. I changed it (one from the junk yard) during the summer. I pulled one of the spark plugs closest one to fire wall on drivers side today and it wreaked of gas but I guess was dry !! and for being a plug only a few months old looked a little ruff. That is probably where it's stumbling a bit I don't know I never have time to do anything

 

I have to ask then does the IAC only really work when using the A/C? What is that little bugger that goes right on top of the plenum underneath the plastic Vortex cover called?

 

As I said, once the engine is warmed up, the IAC really only moves when the A/C compressor kicks on with the engine idling (TPS at ~0.5V output). It may make slight adjustments, but nothing major. The IAC has a lot to do with engine RPM during warm up idling though.

The plastic valve is the MTV (manifold tuning valve). It connects the two different halves of the plenum at higher RPM to reduce the losses due to the long runners.

 

Thanks