I have a 1989 240 that idled smoothly and ran well until I had the engine mounts replaced by a local shop (I don't have a lift). I used new Volvo brand parts from FCP. When the car was returned it idles rough and at any engine speed is coarse or rough running. It starts easily and idles at the normal RPM speed, accelerates well but clearly is VERY different. It vibrates badly at idle but no missing or skipping or surging. I can't see any obvious installation errors. The work did shift the engine position a tiny bit and the tailpipe hits the frame on the right off and on. No error codes are in memory. I see no visible damage to O2 sensor or flywheel sensor but I believe something mechanical happened in lifting the engine to replace the mounts but what? Any suggestions would be appreciated.

 

You purchased the $21 mounts instead of the $6-$10 mounts?

Some aftermarket mounts are stiffer than the factory mounts - so if you did purchase the $21 mounts You could have a broken/sagging transmission mount.

 

I bought Volvo brand from FCP including the transmission mount.