2000 toyota celica gt

yes it has a cel light on its throwing a p0300 and a pending p0303 code and thats it.

it does run better when i first start it up. when it was cold out it had a hard time starting and once it warms up the idle drops real low and starts to idle rough.

Buy a can of carburetor and choke cleaner and start the engine. Spray all of the vacuum lines and listen to the engine for it to stumble or rev higher. The spray where the intake meets the head and the throttle body. The first part sounds like a vacuum leak.

With a multimeter, check the voltage at the coil for #3.

Check the cold start valve or injector for proper operation. When cold, the engine needs a little more fuel than normal for starting and to warm up properly.

Next, perform a compression test. You should see in the area of 150 PSI from each cylinder and no more than 10 PSI variance from cylinder to cylinder. If #3 gives you a significantly lower reading, squirt a small amount of oil in it and check again. If no change, bad valve(s)(not so bad), if compression rises, bad rings(not so good).

Try changing ur air filter and cleaning your mass air flow sensor. Does it feel like a miss fire? or does ur check engine light say "random miss fire"

Closing thread due to lack of response and age of thread.