Had a 6.7 Powerstroke come in with a rough idle and no codes...

The owner said it started about a month ago and was getting worse. We pulled the valve covers and found the rocker arms on cylinders 3 and 5 were just loose enough to mess with the valve timing. After we torqued everything back to spec, the idle smoothed right out. Has anyone else seen rocker arm issues cause problems without throwing a DTC?

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3 Comments

felixk716mo ago

Cylinders 3 and 5 both loose? That's wild it got that bad without a single code popping up.

3

andrew6465mo ago

3 and 5 share the same cam lobe on some of those modular V8s. Bet that lobe is wiped out and the rocker just gave up.

6

joseph4556mo ago

Funny how those mechanical issues can fly under the radar. The PCM is looking for electrical faults in the circuits, not necessarily if a bolt came a little loose. Seen similar stuff on older gas engines where a worn rocker pivot would cause a misfire that the computer just couldn't pin down.

2