JD101b

Today I started up my G550 (M273). Upon startup, the engine felt extremely rough. The vehicle begun to shake from side to side. The check engine light flickered for the duration (lack of consistent power? Alternator issue?) RPM's (with no throttle input) were bouncing between 800-1200 RPM. The engine sounded like a straight piped diesel. After 10-15 seconds, I put the vehicle in park and turned off the car. I waited for about 30 seconds to start the G up again. The second time I started up, the vibrations returned but were far more subdued. I started to drive the car and the vibration and noise ceased.

It should be noted that for the past year or so, the car will, at random, hesitate to start up (it cranks for a few seconds as if it's run out of gas, or the alternator is bad) but I've never had any engine trouble until today. My local dealer checked it out last fall and couldn't find any issues with the battery or alternator.

Not sure what to make of this. Any ideas?

shiann

Any time you get engine shaking, it's usually misfire related. Did you read the stored CEL codes?

My first guess would be ignition coil, spark plug, or spark plug wire on a specific or multiple cylinders.

I also would not drive it if there are strange vibrations coming from the engine.

JD101b

I was running last second errands before going to catch a flight. I didn't have time to read codes (and I don't have a reader - I'll go to my local Autozone and borrow theirs) but it did run fine afterwards. That said, if the problem persists when I get back I'll either buy a code reader or flatbed it to my local MB dealer.

I've always heard that the M273 is a pretty bulletproof engine. Are any of those common problems?

Thanks.