Hey folks,

My motor's RPM bounces up and down while the motor is warming up. I suspect the throttle sensor as being the culprit. Any idea's here...

 

My 91 was doing that.
The warm up fast idle adjustment screw was just a little too high.
After 15 seconds the ECU limits idle RPM to 1500, and the warm up cam was trying to idle at 1800.
I just backed off the fast idle screw to 1500.

Now you know where the Mazda "zoom zoom" ads really came from.

 

Where is the fast idle adjustment found?

 

on the back of the UIM

 

I would check the TPS first, just because its the easier thing to do.

 

Agreed, does the idle still bounce around with the TPS unplugged (assuming S4, of course).

 

I'll check the TPS and then if that don't get it I'll adjust the fast idle screw.... thx