With the car in gear and is not yet warmed up , it idles pretty good . But as it heats up it starts idling rougher . What could this be ??
Engine? Transmission? Mileage? We need as much information as possible to assist.
Sorry , has 201k miles , automatic trans , no codes . Drives fine only idles bad in gear sitting at a light or stop sign .
Dang , it has a 2.0L engine .
The car is 34 years old and there are many things that can cause that kind of problem.
Any vacuum leaks? How old are the air and fuel filters? How old are the spark plugs and what do they look like? The O2 sensor? Have you tried cleaning the MAF sensor, or the fuel injectors? Is compression OK? Etc.
https://www.youtube.com/watch?v=eQpPcdvSBks
https://www.youtube.com/watch?v=1kb-9qLu00Q
Plugs are new-ish , 02 sensor , can it be checked ? I don't know about the compression , but it starts up fast . I don't know if my car has a MAF sensor or something similar .
Not sure on that car, but my '86 Saab 900 has a MAF sensor so they were in use at that time. Uneven compression can cause a rough idle and it should be easy to check on that 4-cylinder engine. O2 sensor should be fluctuating between .1 and 1 volt when the engine is warmed up.
https://itstillruns.com/test-sensor-5193043.html
Another possibility is a worn torque converter in the automatic transmission.
What would cost be to replace a torque converter ??
Thanks for all the the info . I will look into the things mentioned .
It would cost a lot of money to replace the torque converter since the transmission has to be taken out. Probably would cost more than the car is worth. That's a "just live with it" item on a car that old. (Scotty has mentioned that his '94 Celica shakes at idle due to the torque converter.)