So what s next? If the Check Engine light were illuminated, the next logical step would be to connect a scan tool and check for diagnostic trouble codes. Unfortunately, you note no obvious issues. You roll back into the shop and continue following a good diagnostic procedure by performing a thorough visual inspection of items related to engine performance. Based on the symptom, it appears the vehicle has a misfiring cylinder. At least you re not chasing a phantom problem. You road-test the vehicle under a light-to-moderate load and you re able to duplicate the symptom, which is good news.
But today you re up for a good challenge and you can t get to the gravy work until this job is done. Perhaps the thought of a no-code driveability problem signals a difficult day ahead. This occurs mostly under light-to-moderate acceleration and the Check Engine light is not illuminated.
1 A2003 Ford F-150 V8 rolls into your shop, with the customer complaint that the vehicle runs rough at times.
