Brandon Schnautz
Newbie
1997 c1500 5.7l vortec.
Truck has a hard time starting if it sits for about 12 hours or so but it's not consistent, sometimes it fires right up and sometimes it acts like it's not getting fuel, engine only attempts to fire off if you let off the starter and just leave the key on. After you let off the starter it hits but its almost like its dieseling (not actual dieseling like a carb motor does). A new Delphi fuel pump was installed but it did not fix the problem. Key on and engine off it has exactly 55psi of fuel pressure, has the upgraded multi port injector system on it. Coolant residue was found on cylinder #2 plug but I dont see how that would kill all the cylinders on start up and intermittently at that. No mil on at the moment but the 2 codes it has recently thrown were post cat o2 sensor low voltage (new one on the way) and random multiple cylinder engine misfire. It has acdelco iridium plugs with 30k miles or so, the plugs are in decent shape. I have a twin to this truck and all sensor data is identical between the two. I have attached screenshots of the sensor data for this truck (hard starting truck) while it was idling at operating temp. Please note that the o2 voltage levels constantly bounce up and down so the timing of the screenshot makes it appear that they are not reading correctly but they are , water temp was also working but flashing so the gauge appears to not be reading but is.
Truck has a hard time starting if it sits for about 12 hours or so but it's not consistent, sometimes it fires right up and sometimes it acts like it's not getting fuel, engine only attempts to fire off if you let off the starter and just leave the key on. After you let off the starter it hits but its almost like its dieseling (not actual dieseling like a carb motor does). A new Delphi fuel pump was installed but it did not fix the problem. Key on and engine off it has exactly 55psi of fuel pressure, has the upgraded multi port injector system on it. Coolant residue was found on cylinder #2 plug but I dont see how that would kill all the cylinders on start up and intermittently at that. No mil on at the moment but the 2 codes it has recently thrown were post cat o2 sensor low voltage (new one on the way) and random multiple cylinder engine misfire. It has acdelco iridium plugs with 30k miles or so, the plugs are in decent shape. I have a twin to this truck and all sensor data is identical between the two. I have attached screenshots of the sensor data for this truck (hard starting truck) while it was idling at operating temp. Please note that the o2 voltage levels constantly bounce up and down so the timing of the screenshot makes it appear that they are not reading correctly but they are , water temp was also working but flashing so the gauge appears to not be reading but is.
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