2006 R53 S 6sp 157k miles. Driving home from work, I heard a noise like I had kicked up a rock and it bounced along the bottom of the car. Immediately there after acceleration became sluggish, like trying to drive with the brake on. No warning lights, steering and brakes feel normal. Engine revs ok with clutch in or in neutral, but has loud rattle at idle. I'm still trying to track down source of rattle. I assume that something fell off but can't find anything missing. No major engine rocking when revving or shifting gears, so assuming that the engine and trans mounts are ok. Closest dealer is 40 miles away and way overpriced. Anybody run into this before or have suggestions about what might have fallen off?

 

My first thought is that your timing chain tensioner failed, the timing chain jumped a tooth, and now the motor is out of time. Just speculation without any sort of video or anything.

Also, find a local indy shop. Dealerships don't know how to do proper troubleshooting. They just throw parts at cars and hope something fixes it while staying under book time.

 

As far as something falling off, I don't know.
But loss of power under load is usually either a Crank Pulley, a belt tensioner issue that is causing the S/C to not work properly, or an internal S/C problem, but you could easily see if the S/C pulley was not turning. (I'm actually leaning toward Crank Pulley and the noise was actually a piece of the rubber from it)
Generally a Chain Tensor will only make a load rattle, but not cause power issues, and normally the jumping of a tooth will cause the car to not want to run at all.
Get out a long screwdriver to use as, or buy an automotive stethoscope to pinpoint the sound.

 

 

^ Hopefully it's the crank pulley and not timing related.

I haven't personally had either fail yet or have to replace them, but the standard complaint online about a failed crank pulley is a smell of burning rubber as that's what the internal damper is made out of.

 

 

Crank pulley was replaced about 9 months ago. Engine is normal, no lights or codes. No smell of rubber burning.

 

Found the problem. The bolt for the lower mount to the engine bracket is missing and the mount was wedged on the outer edge of the bracket. Now looking for a replacement bolt but can't find the size. Any info on bolt size?

 

M12 - 1.5 x 60mm

 

Thanks.