Engine intermittently misses

Hi,

I was hoping I could get answer to a problem I have with my car. It is a 2002 VW Polo 9n, engine code is AWY.

When the engine is up to temperature, at idle, it feels like the engine is misfiring.

For example, I come to a light, engine starts to idle normally. And then in every ~10-15 seconds it feels like 1 ignition misses. So I feel the engine stutter, but only for a moment. Then it idles fine again for ~10-15 seconds, and then again, like a hiccup.

Also, at these times, if I hit the gas rather quickly to rev up the engine to around 2000-2500, it feels like a cylinder is not working for 1-2 revolutions, but then everything is fine. I can feel the chassis shake a bit, and can also hear this in the exhaust. It sounds like a cylinder is not working. But again, only for like 2 crank revolutions or so.

With the engine running at idle, if I try to remove the oil filler cap, I can feel strong vacuum. If I do remove the cap, the engine starts to shake violently, but does not stall. Pulling out the oil dipstick does nothing. I don’t feel vacuum there.

When moving, everything feels good, the engine pulls as it should. No error codes stored.
I know the oil is way overfilled. It is around twice the level it should be at max. New oil is on the way, so I’ll change it soon.

Please be so kind and let me know what I should check. Or point me to a forum topic that can help me solve this issue.

Topic

[Richard KirshyParticipant]

Possible causes:
Faulty spark plug / coil / wire
Faulty fuel pressure
Faulty fuel pressure regulator
Dirty / faulty injector
Check for clogged / faulty PCV valve

[Author]

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