Toyota Celica Forum:hi idle speed

You probably have a vacuum leak or a bad O2 sensor.  The simple way to figure out if you have a vacuum leak is to soak the vacuum hoses with soapy water.  Start with one hose at a time.  If none of these yield a leak check your EGR valve also.  Unless your "Check Engine" light is on you may not have a bad O2 sensor.

Toyota's also have a high idle (usually around 2K rpm) for a few moments after start up then it dies down to normal idle. Colder it is the longer the idle holds up. Now if it is super warm and it is idling high all the time then there is another issue most likely related to the above post. If you have a Celica GT you have the same motor that is in my car. If not this still applies.

I have the same issue with my 1988 Celica. I have read that the temperature Coolant Sensor might be the cause. Less than 20 bucks to repair

Well that would make sense too since the ecu is determining idle speed based on the temperature of the motor. I thought that was a problem with my MR2 relating to a starting problem (long crank). It wasn't, but it was one of the possible causes.