Compression and leak down test?

Tiny
CHRIS PIERCE2
  • MEMBER
  • 2010 AUDI A5
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
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.
Friday, July 11th, 2025 AT 11:12 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 52,223 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.
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Saturday, July 12th, 2025 AT 10:06 AM

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