Brandon Schnautz
Newbie
1997 c1500 5.7L vortec
For a year the motor has been sluggish below 3500 rpm and after that it takes off like a rocket. Wont do a burnout anymore. Sometimes when starting it spark knocks as if the timing is too far advanced. Was this way for about a year and now it will not start and on the seldom occasion you can get the motor to fire at all, it spins backwards. It recently started to stumble when given throttle when leaving the drive way for the first time of the day. TDC the motor and the rotor is lined up perfectly with cylinder 1. No trouble codes of any kind, no check engine light. Timing chain has not jumped timing. Entire distributor with new cam sensor has been installed, new crank position sensor, coil as well as the ignition control module next to it is new. It has a less that year old Delphi fuel pump that puts out 55 psi at the fuel pressure check port behind the spider on top of the intake (without engine running). All signs point to the computer advancing the timing by a substantial amount while at 'idle' for no reason. My question is what other faulty sensors/ incorrect inputs to the computer would cause the computer to advance the timing like this. There is not any check engine codes nor have there been in the past year so I am flying blind trying to solve this issue. All the new components listed above have been put on in an attempt to remedy the low power at low rpm problem it has had for ~1 year. Also the motor seemed to have full power when cold (leaving the house for the first time that day). So it appears to have a dependency on engine temp but it loses power well before the water temp is at operating temperature.
For a year the motor has been sluggish below 3500 rpm and after that it takes off like a rocket. Wont do a burnout anymore. Sometimes when starting it spark knocks as if the timing is too far advanced. Was this way for about a year and now it will not start and on the seldom occasion you can get the motor to fire at all, it spins backwards. It recently started to stumble when given throttle when leaving the drive way for the first time of the day. TDC the motor and the rotor is lined up perfectly with cylinder 1. No trouble codes of any kind, no check engine light. Timing chain has not jumped timing. Entire distributor with new cam sensor has been installed, new crank position sensor, coil as well as the ignition control module next to it is new. It has a less that year old Delphi fuel pump that puts out 55 psi at the fuel pressure check port behind the spider on top of the intake (without engine running). All signs point to the computer advancing the timing by a substantial amount while at 'idle' for no reason. My question is what other faulty sensors/ incorrect inputs to the computer would cause the computer to advance the timing like this. There is not any check engine codes nor have there been in the past year so I am flying blind trying to solve this issue. All the new components listed above have been put on in an attempt to remedy the low power at low rpm problem it has had for ~1 year. Also the motor seemed to have full power when cold (leaving the house for the first time that day). So it appears to have a dependency on engine temp but it loses power well before the water temp is at operating temperature.
