Burnt valve despite good compression reading? HELP

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Drives: 05 1.2 3 cylinder (6 valve)
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Burnt valve despite good compression reading? HELP

Post by bennyIRE » Fri May 13, 2016 1:18 am

Background: Engine warning light came on in my VW POLO 05 1.2, 3 cylinder (6 valve). Car started jolting forward, struggling and wouldn't go above 30km. Computer showed a misfire in cylinder 3.

Mechanic 1: Put in a new ignition coil but this didn't help. Checked the spark plugs and did a compression test. All fine. He reckoned it was the ECU and quoted €1000 to replace with a second hand one.

I decided to get a second opinion.

Mechanic 2: He thinks it's a burnt out engine valve. Said compression tests don't always show up valve issues in polos. He said it's not the ECU as the issue is temperature based, which rules out the ECU. Quoted e €800 to fix the valve, put a new timing chain in etc.

Question: I can't find anything online about valve issues not showing up on a compression test. Does anyone know what the story is with this? From reading online it seems that the valve issue is much more likely to be the problem, but the compression test has thrown me.

All help appreciated!


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Re: Burnt valve despite good compression reading? HELP

Post by alexperkins » Fri May 13, 2016 6:22 pm

Burnt valve can be masked by a compression test. Depends if it's being done at engine temperature or cold

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