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No compression in cylinder number three

Tiny
ALAZIM
  • MEMBER
  • 2003 BUICK CENTURY
  • 3.1L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 165,000 MILES
DTC PO303-Misfiring and running rough. I replaced coil pack, spark plugs and wires. I performed a compression test and discovered there was no compression in cylinder number three. No fluid on dipstick, however there is a ticking noise coming from inside the engine. What could be the real problem?
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Thursday, November 21st, 2019 AT 12:16 PM

3 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

You need to remove the valve cover and check and see if the rocker arms are moving for that cylinder.

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

As far as possible issues,

1. Burned valve whether intake or exhaust valve.

2. Piston damage not allowing build-up of compression.

3. Broken valve spring on one of the valves.

Roy
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Thursday, November 21st, 2019 AT 12:45 PM
Tiny
ALAZIM
  • MEMBER
  • 2 POSTS
Dear Roy. Sorry for the late reply. As you suggested; I pull the valve cover and discovered an unseated rocker arm (see photo). I decided to replace both heads and gaskets. Thanks
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Monday, November 25th, 2019 AT 6:06 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good deal.

Roy
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Monday, November 25th, 2019 AT 6:19 AM

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