I have a 07 mini Cooper base model that is rough running until 3000 rpm took to mechanic and he told me cylinder 4 wasn't firing. Then turned around and showed me the compression for cylinders 1,2&3 were 175lbs and cylinder 4 was 125 can anyone let me know what correct compression should be and if cylinder 4 is actually low or is 1, 2 and 3 high
THANKS IN ADVANCE

 

Sorry to say no 4 is very low,the other 3 are within acceptable condition,would point to any of the following,failed head gasket,cracked head at the valve seat area,or a warped head,all mean the head will have to removed for investigation and repair or replacement,personally I would look for a replacement or reconditioned head,and replace yours along with a full gasket set,sorry but the age of the car may prove to be not economical to repair unless you can get it done by your local college that teaches auto repair that will save on labour cost.

 

Ok thanks so much