V-8 Engines With Slight Rough Idle - Adjust Spark Plug Gap - BQMI
| Subject: | V-8 Engines With Slight Rough Idle - Adjust Spark Plug Gap |
| Models: | 2007-2008 Cadillac Escalade |
| 2007-2008 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer |
| 2007-2008 GMC Savana, Sierra, Yukon |
| 2007-2008 Hummer H2, H3 |
| with 4.8L, 5.3L, 6.0L, or 6.2L V-8 Engine |
| (RPOs L76, L92, LC9, LH6, LH8, LMF, LMG, LY2, LY5, or LY6) |
This PI was superseded to update Recommendation/Instruction. Please discard PIP4404.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may complain of a slight rough idle with no DTCs or additional engine performance concerns and comparison vehicles may exhibit the same concern.
Recommendation/Instructions:
If the SI diagnostics do not isolate a cause for this concern, remove all 8 spark plugs, adjust them to the maximum gap of 0.045" (1.143 mm), re-install them, and re-evaluate the concern. This adjustment may make the rough idle less objectionable. Any remaining roughness should be considered an idle characteristic of the engine.
Notice: Do not clean fuel injectors to address this concern unless the AFIT (Active Fuel Injector Tester) detects an imbalance when the SI diagnosis is being performed. If any injectors are cleaned, please fax a printout of the AFIT readings before and after cleaning to Jay Dankovich @ 586-947-9503.
Notice: The spark plug gap adjustment above should only be attempted if the customer complains of a rough idle and SI does not isolate a cause for it. It will not repair any other symptom.
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.
