Originally Posted By: browning300wsm
i worked 30yrs. for GM
You didn't check for TSB's?
Engine - MIL ON/DTC P0300/Engine Misfire
Notes
Bulletin No.: 04-06-04-081C
Date: August 18, 2005
TECHNICAL
Subject:
Check Engine Light Illuminated, Engine Misfire, DTC P0300 Set (Replace Exhaust Valve Springs and Seals)
Models:
2004-2005 Chevrolet Colorado
2004-2005 GMC Canyon
with 2.8L Inline 4 Cylinder or 3.5L Inline 5 Cylinder Engine (VINs 8, 6 - RPOs LK5, L52)
*For Engines Built Before and Including VIN Breakpoint 58261313 and Build Date 04/13/2005
*This VIN should ONLY be used in conjunction with the Dealers checking the Engine Unit Number (EUN) (label date reads T050880001 or lower) if they think they have a truck exhibiting the issue.
Supercede:
This bulletin is being revised to update the VIN breakpoint and Engine Unit Number. Please discard Corporate Bulletin Number 04-06-04-081B (Section 06 - Engine/Propulsion System).
Important: The bulletin may apply to vehicles with a VIN breakpoint of 58261313 or lower. If the last 8 of the VIN is lower than 58261313, the engine unit number (shown in SI # XXXXX) will have to be inspected to determine if the bulletin applies. If the engine unit number is XXXXX thanNNN-NN-NNNNthe bulletin applies to the vehicle. If the engine unit number isNNN-NN-NNNNor greater, the engine already contains the updated valve seals and springs that are mentioned in this bulletin, so the bulletin does not apply.
Condition
Some customers may comment on a Check Engine Light On or that the Check Engine Light is flashing. An actual engine misfire may or may not be felt. Typically this occurs during engine warm up or on deceleration after the engine is at operating temperature. Additionally, some customers may comment on a light engine knocking noise or misfire during warm up or on a deceleration after the engine is at operating temperature. Upon investigation, the technician will find a misfire code P0300 through P0305 and possibly a P0420.
Important: If a DTC P0420 is stored along with DTC(s) P0300 through P0305, the catalytic converter diagnostics in Service Information (SI) must be followed to determine if the catalytic converters are operating properly.
Correction
Perform the diagnosis for the P0300 DTC as found in the appropriate section of Service Information (SI). If no concerns are isolated through the diagnosis, then replace all of the exhaust valve springs and seals. It will be necessary to remove the intake and exhaust camshafts. Refer to and copy all of the appropriate section(s) of Service Information (SI) repair procedures referenced below before attempting this repair. Refer to the parts information below to determine what bolts, valve springs, seals and gaskets will be necessary during reassembly.
