Check the air supply, make sure the filter is clean and that the intake is clear.
I would first check your PCV valve, this was cracked on my 93' Celica GTS and caused that problem. It's very ease and cheep to fix. If this doesn't seem to be the cause of the problem I would check your air intake hose and vacuum lines.
It could be a dirty air filter or a dirty throttle body.
I couldn't figure out how to add more info to this question, so here goes: My 2005 Celica will occasionally idle so low the car shakes a little, tach shows maybe 400-500rpm. It will then seem to realize this and up the idle back to 800-900rpm. Then it will cycle between the two every few seconds. This happens rarely, maybe once every other month. If I put the car in neutral the problem goes away and idles around 800-900rpm. Never had any problems with acceleration or when at driving speeds. My car has an automatic transmission and around 65,000 miles. 50/50 mix of city/highway driving. Castrol GTS 5W30 oil. I can't think of any other pertinent info, let me know if you need more. Thanks, -Farrell
Very vague information. Could be the main jet in the carburator.
Listen and look for a vacuum leak. Could be anywhere.
Timing belt could be bad and could have jumped a tooth or you need a toon up.
Could be clogged converter in the exhaust system..
idles at 3000 will not go down 1993 grand prix gtp
My 1990 idles at about 850 and with the ac on 1100
Cinnamon Idles was born on October 26, 1975, in Chicago, Illinois, USA.
see previous answers, but if it idles high it might be the Mass Airflow Sensor. if your car idles too high for too long and you keep driving it, you could burn out the transmission module (very expensive )
I had the same problem with my 95 celica gt convertible. Turns out, the idle air control valve goes out on these things and you have to replace it or you just wont have any power...i.e. it stalls. The part costs $250, but you can find it online for $90.