1999 C30 454 auto misses when cold at 3500 when it gets warm it misses at lower rpm. Fine below 2000. New plugs wires dist rotor cap. No codes reported.
Country: United StatesMake: GMModel: C30Year: 1999Engine: 454
main cpu swapped
Thanks for trusting us with your problem. I have trained in the automotive field and currently work as a shop foreman. I will be helping you today.Test for 30KV available from the spark plug wires. If spark is erratic or not present, check the other cylinders. If OK on some cylinders, but not on others, replace the distributor cap.If spark is OK, check fuel injector balance using the scan tool and a pressure gauge. All 8 fuel injectors should drop fuel pressure equally. Remove the front O2 sensors and check for misfire now. If now OK, check for a restricted catalytic converters. If the above is no help, temporarily shim the Crankshaft Position sensor with a paper clip, between the sensor flange and the front cover mounting surface. Recheck misfire with the shim in place. If now OK, permanently shim the CKP sensor with 1 or 2 shims, (if needed), part #12565102.perform CKP learn after shimming and/or replacing the CKP sensor. CLICK HERE for relearn
When the scan tool is connected and you are in CKP learn mode the vehicle will not start when key is in crank position. Thanks