I have a 98 civ ex that when it switches into closed loop the idle dances back and forth between 1100 and 1900. Atop the throttle body there's a piece of electronics that appears to be some vacuum reading sensor. Unplugging any other sensor has no effect on the dancing idle but this sensor on top... if i unhook it, the car almost dies... but comes back, upon being hooked back up the car seems to find its idle.

1. wtf?
2. what is that sensor atop the throttle body?

The maf seems to play no role in this.

I appreciate any help you can give me.

 

That should be your MAP sensor. It detects the amount of vacuum being generated inside the intake manifold. You likely either have a leak somewhere around the IM that's letting air get in around the throttle body or the idle isn't set correctly.

 

and that's just a screw on the TB, correct?

 

I took off the entire throttle body, separated the iacv and cleaned the whole deal. when i put it back on there's no difference.

but 2 things to note:

When i turn the a/c on, the idle stays steady

When i unplug the iac sensor, nothing changes.


I'm guessing that means the IAC is shot?