Said It Here

How to tell if low compression is bad piston rings

Low cylinder compression and blowby are often caused by stuck or worn piston rings, but diagnosing them at home requires sorting through symptoms like persistent misfires when other parts have already been replaced. Without funds for a professional mechanic, trying to pinpoint the mechanical failure yourself leaves you stuck guessing whether the rings are simply gunked up or require a full teardown.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    replacing parts like fuel injectors, coil packs, spark plugs, O2 sensors, and the alternator
  2. 2
    performing a compression test
  3. 3
    trying to do repairs independently instead of hiring a mechanic

In their words

Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.

r/AskMechanics1 person · September 2026

“Trying to diagnose blowby. Compression on this cylinder is only at 90.”source ↗

“Does this ring look like its gunked up or bad?”source ↗

kittC4T · r/AskMechanics · 1 upvotes
r/MechanicAdvice1 person · September 2026

“My fiance has a 2014 Honda Accord 2.4. It has an isolated misfire on cylinder 4. I have replaced fuel injectors, coil packs and spark plugs, Upper and lower 02 sensors, and alternator. It had a engine replacement and then went about 40,000 before limp mode. Im just looking for next steps to try and figure out whats next.”source ↗

New-Ad1643 · r/MechanicAdvice · 1 upvotes

“We dont have the money for a mechanic at the moment. Which is why over like 2 years ive been trying to do it myself”source ↗

New-Ad1643 · r/MechanicAdvice · 1 upvotes

Where this came up

People with this problem also raised