Air fuel

[Gilbert Marquez]

1990 c1500 runs real good when cold but once it heats up to operating temp check engine comes on n starts running rough and loss of power and sometimes will not start only crank. Any ideas?

[richard wysong]

maybe problem with the coolant temp sensor? any codes? check for a vacuum leak at the base of the throttle body. what engine? maybe bad MAP sensor? Fuel filter? any gas in the oil? Bad Ignition coil? You need to see what code is causing CEL. could also be clogged cat and other things

Edited September 16, 2022 by richard wysong

[Gilbert Marquez]

Check eng light is on but not throwing any codes. Changed, erg valve, tps,map sensor,02 sensor. Ever since I changed out these parts it runs even worse. Starts up fine then idle starts fluctuating real bad til it finally just dies.

[richard wysong]

if the CEL is on but no codes the ECM would be suspect. How are you trying to pull codes?It sounds like you have a vacuum leak some where. Check the base gasket on the throttle body by spraying brake or carb cleaner around it

[richard wysong]

What engine?