| Subject: | Hot Hard Start, Black Smoke, or Brief Rough Running |
| Models: | 2005 Buick Rainier |
| 2005 Chevrolet TrailBlazer |
| with 4.2L Engine (VIN S - RPO LL8) |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
On rare occasions, a brief rough running, hard start, and/or black smoke concern may be noted when restarting the engine after a brief hot soak. Typically, this will occur after a 5 - 20 minute hot soak and no DTCs will be present. If the engine is hard
to start, slightly opening the throttle normally improves engine starting. Once the engine starts and runs for a minute or so, these conditions normally diminish. Additionally, the injector pulse width may be as much as 3 times higher than expected if it is
monitored during the concern.
Recommendation/Instructions:
If the SI diagnostics do not isolate a cause for this concern, reprogram the PCM with the latest TIS calibrations.
On April 17, 2006, an updated PCM calibration was released on TIS2000 satellite update version 4.5 (2006) to address this issue. The updated PCM engine calibration is titled "New calibration to address customer complaint of hard starting or black smoke
on start up". This PCM engine calibration, or any that follow, is designed to address this issue. As always, make sure your Tech 2® is updated with the latest software version.
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.
