Low compression?

Tiny
BESTSWJ@GMAIL.COM
  • MEMBER
  • 2012 AUDI A4
  • 2WD
  • 100,000 MILES
I bought a used car just 3 weeks ago. After 2 or 3 days of purchasing the car, car started shaking on driving. Once the car had sign of engine and stopped, was moving to mechanic by a tow truck. The mechanic changed 4 spark plugs and it was pretty good for a few days, however, it start shaking a bit. The mechanic said it would be a piston ring problem. When he scanned the car, the compression was low in second cylinder and the spark plug was with oil. I don't know about a car at all and I'm in panic now. Please give me some information about what I should do. Thank you.
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Saturday, December 19th, 2020 AT 8:44 PM

2 Replies

Tiny
KASEKENNY1
  • EXPERT
This does sound like a possible compression issue but we need to check that with a gauge. You can't get compression by scanning the vehicle so we need to actually check the compression and see what it is. Here is a guide on how to do that:

https://www.2carpros.com/articles/how-to-test-engine-compression

Depending on what the readings are we can go to the next step. However, the other likely cause here is a vacuum leak.

Here is a guide on how to check for a vacuum leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let us know if they gave you the readings on the compression test if they did do one and we can go from there.

Lastly here is a guide on changing piston rings if we go that route:

https://www.2carpros.com/articles/replace-engine-piston-rings

Thanks
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Monday, December 21st, 2020 AT 5:42 PM
Tiny
KEN
  • ADMIN
Is it only has 100,000 on it I would start by removing the cylinder head to see if any of the valves are leaking, you can also find out more by having a leak down test done which puts pressure into the cylinder to see where it is going. A valve job may fix it. Here is how to remove the cylinder head in the diagrams below. Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.
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Monday, December 21st, 2020 AT 5:52 PM

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