Low Compression on all 4 Cylinders
Posted by BlackMan4321@reddit | projectcar | View on Reddit | 8 comments
I have a b18b1 engine and it has low compression (120psi) on all cylinders and have zero clue what to start looking at to fix it
Poil336@reddit
Ok, hang on, why were you doing a compression test? What's actually wrong here? Peak compression numbers will vary due to a couple different factors, but the variance between cylinders is just as important.
chuckms6@reddit
I could argue that variance is more important that the average, the only thing a low average points to is total sealing failure of the head gasket. Compression test is usually used to determine which cylinder is having issues and those issues are confirmed with a leakdown test. OP is freaking out about a number that means nothing without context.
Raving_107@reddit
Head gaskets usually affect one or two cylinders depending on where it gave out or how the head warped. Even compression loss among all cylinders points toward a timing chain/belt issue.
BlackMan4321@reddit (OP)
I believe the car is misfiring because the cat is melted so i was just troubleshooting
Poil336@reddit
The cat being melted will cause misfires, I don't think you're chasing a compression problem. Free the exhaust up and re-evaluate
rudbri93@reddit
does it come up with a little oil in the cylinders? whats spec for compression on that engine?
BlackMan4321@reddit (OP)
No oil comes up and it should be around 180-200
Millpress@reddit
Retest it with a little oil in the cylinders. If it comes up it needs rings or the rings were fuel washed and not sealing well.
Check the valve lash, tight valves won't seal well. Check can timing and verify that the timing belt is installed correctly.