No compression in cylinder five

2002 TOYOTA 4RUNNER
387,000 MILES • 3.4L • V6 • 4WD • AUTOMATIC
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ZINODAVIDOFF54
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Suddenly lost compression on an interstate highway, and felt rough but primarily noticed when at exit stoplight. Still runs and drives. Soaked the cylinder with cleaner for several days but no change.

Wondering if there’s any benefit to trying “Engine Restore” or Lucas or something before replacing the engine (too many miles and too costly to just rebuild or do valve job).

Thank you for any advice.. deeply appreciated.
Nov 30, 2019 at 11:15 AM
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ASEMASTER6371
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Good afternoon.

None of that stuff works.

Did you use a compression gauge for the test? If you did, what is the compression?

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

Possible reasons:

Burned valve

Broken piston rings

Broken piston.

Broken valve spring not allowing the valves to close.

The way you can tell is by removing the spark plug and insert shop air into the cylinder and listen to where the air leaks out.

Roy
Nov 30, 2019 at 11:30 AM