Compression and leak down test?

2010 AUDI A5
160,000 MILES • 2.0L • 4 CYL • 2WD • AUTOMATIC
Avatar
CHRIS PIERCE2
  • MEMBER
  • 1 POST
When I did the compression test. The results showed no compression on cylinder 1. But during the leak down test, at TDC it passed the test. I'm trying to pinpoint exactly what the issue is. About a week ago the car shut down while driving about 40mph, was told it seemed like it run out of gas. Had it towed home and replaced the PVC valve/oil separator and now it cranks again but very rough idle and drive.
Jul 11, 2025 at 11:12 AM
Advertisement
Avatar
CHRIS PIERCE2
  • MEMBER
  • 1 POST
I'm trying to pinpoint exactly what the issue is. About a week ago the car shut down while driving about 40mph, was told it seemed like it run out of gas. Had it towed home and replaced the PVC valve/oil separator and now it cranks again but very rough idle and drive.
Jul 11, 2025 at 11:45 AM
Avatar
STRAILER
  • CERTIFIED EXPERT
  • 53,854 POSTS
I don't understand how the #1 can have no compression but pass the leak down test? One of these test must be off. Here is a guide that shows the causes of no compression. The engine will need to have a bore scope inserted to see what went wrong inside the cylinder.

https://www.2carpros.com/articles/the-reasons-for-low-compression

Please go over this guide and get back to us.
Jul 12, 2025 at 10:06 AM
Advertisement