P0300 code

[Garrettwess]

Hi I have 2003 Chevy Silverado 1500hd. Let me start from the beginning last August I replaced gaskets on the valley cover, intake manifold and valve covers. while I was down there I replaced spark plugs, wires, knock sensors and harness aswell but in the process of that I accidentally snapped a evap line that connects to the purge valve and goes down by the fire wall and have not replaced it yet and haven’t really had much problems until last night. it started idling pretty rough and the check engine light started flashing and has not gone away I plugged in a scanner and I’m getting codes for p0300 (random multiple misfires) and p0332 (knock sensor bank 2) so what could be throwing those codes would it be the evap line, injectors, coils, etc.

[asilverblazer]

11 hours ago, Garrettwess said:

...I accidentally snapped a evap line that connects to the purge valve... and have not replaced it yet and haven’t really had much problems until last night... I plugged in a scanner and I’m getting codes for p0300 (random multiple misfires) and p0332 (knock sensor bank 2) so what could be throwing those codes would it be the evap line, injectors, coils, etc.

1. What do you mean by "haven't really had much problems", either the truck runs fine with no check engine light or it doesn't.

 

2. Investigate the knock sensor first, the truck won't be able to adjust timing correctly without it. Poor timing can cause miss fires. Fix the EVAP line, obvious faults will complicate diagnostics.

[Garrettwess]

It’s had a check engine light for awhile because the cats are cut and throwing code for 02 sensors it ran fine until like I said check engine light started flashing and getting bad idle I’ve not had these codes before besides the 02 sensor I’ll get the line replaced and for the knock sensor should I replace them see if that works 

[asilverblazer]

4 hours ago, Garrettwess said:

...for the knock sensor should I replace them see if that works 

I would have a new on hand - I would inspect the old one for damage and check wiring to it - if you are tearing it down to check the old one, might be just as easy to replace it while you're there.

 

I don't have the actual diagnostic for it in front of me to confirm that a new knock sensor is the correct action for P0332. 

 

There is also an outside chance that something else could be causing weird engine "vibrations" that the sensor(s) are picking up as miss fires. If memory serves, bad motor mounts, loose components, accessory drive issues or other drivetrain faults such as out of balance tires even. None of these are nearly as likely though and I wouldn't consider until thoroughly diagnosing the knock sensor issue.