repair shops

My 2000 Buick Leaves custom has an engine compression problem with cylinder #4. Neither the Chevy or Ford repair shops can tell me exactly what's wrong. In reverse the car vibrates harshly. In idle it vibrates harshly. When driving it runs good on 5 cylinders. My wife has a good car but if my...

Praise report!!The other day, I had a problem with a car tire ,there was a hissing noise, and the air pressure was at 19 lbs. and falling rapidly. I didn't see a nail{the usual cause.} it was like 7 pm. after the repair shops close, and if I put air in the tire, if a nail, it would only go flat...