Hey guys. In my time here I've never seen this "issue" before and I am wondering what could cause this to happen:

I had my car hooked up to STAR today at a local shop (got an SRS malfunction), with the hood open to the 90 degree point and the engine running with the A/C on. The engine was vibrating/shaking pretty noticeably. The guy who was scanning the car noticed it and said "that's too much shaking" and asked me several maintenance questions.

-The plugs are 43,000 miles and about 19 months old.
-The engine mounts (all three) are less than 15,000 miles old.

The STAR scan shows no trace of there ever being a misfire or fuel trim issue or anything like that. The engine was running perfectly. It was on top tier 93 octane fuel and there was no sputtering from the engine/exhaust and no abnormal noises. I looked up youtube videos of other M271s running and sure enough none of them shake like mine was. Anyone have any ideas as to what I could look for?

 

How bad is it with the A/C load off the engine?

Throttle body actuator would be my primary suspicion.

 

I will check later today about if the A/C running makes it happen. It is not noticeable from the cockpit - can't feel a thing. Only visual once you open the hood.

Would the throttle actuator cause a pending/stored code? Nothing was present and no symptoms of anything amiss.

 

No - the damn throttle actuator can oscillate without throwing a code. Only fix is a new throttle body.

 

Okay well that doesn't sound like fun but as it seems to be running/driving fine I am not going to worry about it. I am, however, going to see if the A/C load is to blame. Will post back and update.

 

It is only present when the A/C is running. No noises from the belts or compressor, though, and the idle is stable.

 

Don't worry about it then.

 

Matt that's normal for a tractor engine

 

Matt won't be happy until he finds a problem, even if there isn't one.