V-8 Engines With Slight Rough Idle - keywords 4.8 5.3 6.0 6.2 engine L76 L92 LC9 LH6 LH8 LMF LMG LY2 LY5 LY6 RPM vibrate vibration
| Subject: | V-8 Engines With Slight Rough Idle |
| Models: | 2007-2008 Cadillac Escalade |
| 2007-2008 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer |
| 2007-2008 GMC Savana, Sierra, Yukon |
| 2007-2008 Hummer H2 and H3 |
| Equipped With a 4.8 5.3 6.0 or 6.2 V-8 engine. |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
A dealer may encounter a vehicle with the customer concern of a rough idle. There will be no other driveability concerns or DTCs associated with the rough idle.
Recommendation/Instructions:
Complete the current SI diagnostics for any DTCs or symptoms found. The condition described in this PI is a slight vibration that may be objectionable to the customer. Comparison to a like vehicle may reveal the same type of rough idle.
Adjusting the sparkplug gap to the maximum specification of 0.045 in/1.143 m/m may make the rough idle less objectionable.
Note: This sparkplug gap adjustment should only be attempted if the customer has a concern of a rough idle. It will not repair any other symptom.
Evaluate the rough idle after the sparkplug gap has been adjusted on all 8 sparkplugs.
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.
