Mk2 Leon Cupra Bwj 2007 low compression

[Crezzlin]

Any advice guys, low compression on all 4 cylinders, around 60-75psi on all, car has 106k on her and starts fine but have had some random misfires that come and go. Was going to change belt and chain this week but thought I'd check compression first Thanks

 

[R3k1355]

Seems kind of strange for it to be down on all 4 cylinders, one or two cylinders might indicate a problem, but all 4 is either a massive problem or a fault with the testing procedure.

 

[mty12345]

Seems kind of strange for it to be down on all 4 cylinders, one or two cylinders might indicate a problem, but all 4 is either a massive problem or a fault with the testing procedure.

I agree. Is it possible that timing has jumped slightly so that valves are closing late or opening too early?

 

[R3k1355]

I agree. Is it possible that timing has jumped slightly so that valves are closing late or opening too early?

Yep certainly possible, obviously if that has happened you're in danger the pistons have hit the valves and caused damage.

 

[Crezzlin]

Thanks, everyone. I bought a second compression tester, ran the engine dry, removed the spark plugs, and tested all cylinders—same results as before. After removing the Schrader valve, I’m now getting 120 PSI across all four cylinders. I also replaced the spark plugs, and the misfires are gone. The engine starts up easily every time, there’s no smoke, and it's drawing proper vacuum from the oil filler cap.
Next up: I’ll be replacing the timing belt and chain this week and performing a B-12 cylinder flush. Fingers crossed!