polo uneven idle / compression

[flat4fanatic]

Hi all, hope you might be able to help. I got a 2002 BBY 1.4 16v polo off a friend 78k miles. He had some issues with intermittent idle. It drove 100 miles home absolutely fine, then some days later the problem came back. It runs ok when cold but when up to normal temp after about 15mins idling it starts rough.

It was giving the following code: 16686 / p0302 on number 2 cylinder. If you clear the codes they eventually come back.

I changed the plugs as I had some and a mate gave me a brand new coilpack to try as a test. Also tried swapping the injector for one from a different cylinder.
One odd thing I noticed was the metal clip holding the injector to the plastic rail on no 3 was missing

None of these fixed it. I got a compression tester and with 10 seconds cranking on each cylinder got the following: 1: 200, 2: 178, 3: 203, 4: 200. I tried a bit of oil down the bore and the compression test gave the same result. The top of the piston in no2 looks dirtier than the others
Could this be valves on no.2?

Any ideas / advice appreciated.

Thanks,
steve

[niall campbell]

Could be spark plug

I would change plugs and coil packs & monitor oil consumption

[Crasher]

Exhaust valve guide wear and subsequent valve seat burning are a common problem on these engines, it all points to a number 2 burnt valve. If you can get it when it is running on 3 and showing the fault code, try clearing the code with it running. If the misfire clears for a while, the head needs to come off.

[flat4fanatic]

Thanks, will try that at the weekend

[flat4fanatic]

Thought id update this for future reference. Took the head off. Machine shop found 2 exhaust valves almost solid due to worn valve guides. Got all new exhaust guides, valves lapped, vac tested and a head skim done. Back on with new cambelt, ran it up, cleared codes and seems to be idling well on all 4. Bit of a stutter coming off revs for a couple of seconds so cleaned out throttle body, a mates going to reset that at the weekend, otherwise its an air leak somewhere, but so far so good