cylinder 3 low on compression

[Sprinting Clio]

Due to my 172 having a lumpy idle and i need the belts doing and seems its £100 more for a specialist to do it then me, To make sure i didn't waste my money by getting the belts done then needing to take the head off and after seeing a few posts i decided to do a compression test after work

cylinder 1 180psi cylinder 2 175psi cylinder 3 130psi cylinder 4 175 psi

going to do a leak down test 2moro if i can get hold of the tool which is the most common fault valves or piston.

 

[stevescort172]

The chap who did a compression test on my engine he was buying sprayed it with wd40. Is number three a common one, what was the spark plug like??

 

[danielbarton94]

Any luck buddy?

 

[Sprinting Clio]

Ok weird one can't of had the tool screwed in properly. As last night redone the compression test and got 180 psi on cylinder 3. I didn't put oil in the bore or anything just a straight test

 

[Beasley Clio182]

possible bad connection on the tester? or a valve issue? not sitting right ie bad valve seat or bent !