1994 Chevy Corsica Check Engine Soon

TD838

MEMBER
1994 CHEVROLET CORSICA
6 CYL
FWD
AUTOMATIC
121,051 MILES

My Check Engine Soon light comes on. The fast idle is too fast upon startup. Could these two problems be related to a common problem? Also, I disconnected my batter terminal so that the computer can reset and roboot its settings. The car then runs smooth until some time goes by then the fast idle races at startup again and my check engine light comes back on.

Thanks

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

Hi td838 and welcome to 2carpros

Too fast an idle speed. If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft and a defective idle speed speed control motor/valve stuck in the extended (high idle speed) position/throttle position sensor. Also the throttle plate could be binding in its bore and kinked accelerator cable, coolant temperature sensor might not be operating properly misleading the computer that the engine is still cold and computer throwing fuel at it raising the idle speed.