99 4cyl - Idles up at stop

Hey all,

I have a 99 Tacoma 4 cylinder with about 62,000 miles on it. When I come to a stop the idle will jump up briefly and then come back down to normal (about 1000rpm). It does NOT surge over and over again, rather just jumps up once.

There are no other idleing issues, other than this everything is great.

I removed the throttle body and IAC and cleaned them all out. Didnt help.

 

Isn't there a vacuum line that feeds the IAC? Maybe the port for it is clogged on the interior of the intake manifold. There by not allowing it to get enough vacuum to compensate for the idle change when you pull up to lights.
Pull the vacuum line and use a straw from a spray can to clean it out and maybe spray some carb cleaner through the port for good measure.

If that doesn't work the IAC maybe bad

 

Still not resolved, but I'm back on the case.

Latest culprit is the "Throttle Positioner" which consists of a diaphragm that gets a vacuum from the throttle body and pulls a plunger off the throttle. It is located just under the throttle body. If no vacuum is present, the plunger pushes away from the diaphragm and opens the throttle. A loss of vacuum here could easily be my problem. Ive looked for a vacuum leak with propane, but cant find anything.

Does anybody know anything about this? My next path is to check the TPS and the gap between the set screw and the plunger as directed by the Haynes manual.