Vehicle: 2016 Volkswagen Jetta Sedan (163), L4-1.4L Turbo (CZTA), Automatic Transmission/Transaxle
Mileage: 48,235 miles
Problem: The VDub was in the shop because the malfunction indicator lamp (MIL) was on, the engine was intermittently running rough and lacked power.
Case Details: The tech connected a scan tool and retrieved the following diagnostic trouble codes (DTCs):
- P0300 - Random, Multiple Misfires Detected
- P0301 - Cylinder 1 Misfire Detected
- P0302 - Cylinder 2 Misfire Detected
- P0303 - Cylinder 3 Misfire Detected
- P0304 - Cylinder 4 Misfire Detected
He removed and inspected the spark plugs. They all looked new and everything else in both the ignition and injection system checked out good. Compression was in specs. It was time to call ALLDATA Tech-Assist.
The Tech-Assist consultant advised that since the mileage was low and there seemed to be no ignition, fuel or compression issues, the tech might want to try a combustion chamber cleaning. It’s common for these engines to build up carbon on the valves which can cause the issues he was describing. The consultant further recommended verifying the problem with a vacuum gauge by watching the needle to see if it fluctuates at all.
Confirmed Repair: As anticipated, the vacuum gauge needle did fluctuate abnormally. The tech performed a combustion chamber cleaning, cleared the DTCs and reconnected the vacuum gauge. This time, the needle was steady. A good road test confirmed the repairs. Problem Solved!
The ALLDATA Tech-Assist team fields cases like this every day. See how Tech-Assist can help your shop save time and money with on-call diagnostic support from ASE-certified Master Technicians. More Tech Tips
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