[chubbychaser627]

I have a 92 tercel automatic 92k miles. When you first start it up it idles fine for about 30 seconds but then begins surging up to approximatley 1750 rpms and back to 750, it continues to do this until you place it in gear. When the car is in gear you dont notice the engine surging. I am not sure what causes this issue any suggestions would be greatly appreciated. The engine runs well even when the idle speed is fluctuating

 

[chronoti]

check for loose vaccune lines and maybe cleaning your tb might help.

 

[kene]

i had the same problem..here is what it is:

It is actually a vacuum leak located where the the intake manifold meets up to the engine head(on the reaer side of the motor) between cylinder #1 & #2. the way i found this out was to spray some brake cleaner at different areas on the engine while it is idling. when i hit that spot the engine revs went down. If I sprayed a whole lot directly at it the engine would almost shut off.