Subject: | GEN III or Gen IV V-8 Engine Misfire |
Models: | 1999-2007 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer |
2007 Silverado Classic Body Style |
1999-2007 GMC Envoy, Savana, Sierra and Yukon |
2007 Sierra Classic Body Style |
This PI was superseded to update model engines. Please discard PIP4138.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
An engine misfire that may be caused by lifter roller or camshaft wear on any 4.8 5.3 or 6.0 V-8 engine.
The misfire described in this PI may be difficult to diagnose, hard to feel, and can occur on any cylinder.
Engineering is interested in any of these concerns and may want the old parts returned. (please see note with contact information at the bottom of this PI)
Complete the current diagnostics for any symptom or trouble code found.
If the vehicle is showing misfires on a single cylinder, and the SI diagnostics are inconclusive, there may be a valve train, or camshaft related concern.
General Motors Brand Quality and Engineering is interested in any V-8 engine with a cam lobe or lifter concerns. This would include any excessive wear to the lifter roller, or the cam lobe itself.
A complete compression test, an injector balance test, and a cylinder leakage test must be completed and documented. If these diagnostics are inconclusive, continue with the information found in this PI.
Valve train concerns that are causing difficult diagnostics are listed below, and the tests and/or inspections should be completed by the easiest to find to the most difficult.
Thoughts on root causing some of the misfire concerns that may be encountered.
Note: In the event a flat spot or pitting is discovered on the lifter or cam, please contact Brand Quality Manager Jay Dankovich to discuss the repairs, and parts returns.
Note: Contact can either be made by E-mail or phone call.
Note: Jay Dankovich jay.dankovich@gm.com Cell Phone 586-947-8881
Note: When contacting Jay Dankovich the root cause should have already been found. Engineering is looking only for cam lobe or lifter concerns.
Note: When diagnosing a misfire on a GEN III or GEN IV engine, and a cylinder head has been removed, replacement of that bank of lifters (if only one head is removed replace only those 8 lifters) is suggested.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.