1993 Chevy Corsica engine idles high when cold

WAYPASTDAWN

MEMBER
1993 CHEVROLET CORSICA
6 CYL
FWD
AUTOMATIC
142,000 MILES

I have been working on my daughters car. When its cold it idles over 1000 rpm until it warms up. I found 2 codes in the system one being tps too low and egr bad reading. No check engine light is on. Also the other day on her way to work it died and would not restart. She was at a stop sign when it happen. After a short while it started again and was able to make it home. I hook up a mt2500 snap on scanner and check the codes that are listed above. I also check the sensor data and it show only 75 rpm but the desired idle showed 825 rpm I changed the crank sensor it did noot help. I aslo change the iac, tps and I do think I solved the idle problem I wont know until tommorow. When it has cooled off. I also check the fuel pressure it went up to40 psi when turing the key on and then styed between 36-40 psi while running. Slightly low according to specs. Have I miss anything?

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

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.