Morning,

More car woes. The wife's Polo (1.2 12V 2005 3 Cylinder) started to run lumpy and flashed the warning about misfires.

I took out coil and plug 1 as I suspected this cylinder and started the engine, and it ran the same. I took out coil and plug 2, replaced 1 and restarted and it was really lumpy, feeling like it was firing on one cylinder. I put it all back together fired it up once more and its now really lumpy like its still one cylinder.

I've ordered 3 plugs and 3 coils on the off chance that I broke the middle one when removing it.

Anyone got any other possibilities? Have I totally knackered it with this little test?

I've Googled and a common fault could be a burnt out exhaust valve, in which case I'll scrap it.

TIA

Jon

Morning Jon


I'd do a compression test when you have plugs out to fit the new ones. Have you read any fault codes? If it is a valve I don't think it would be that difficult to wip the head off.

Gary

Seems a sensible place to start.

Could do a compression test on the cylinders to see if something has popped.

I'm close if you need a helping hand though I haven't got a compression tester I'm afraid.

Steve

clubpolo.co.uk is very good

I was going to write about common polo problems, but all the ones I know are for the 4 cylinder.

however a quick search indicated it might be the timing belt has stretched
https://www.driftworks.com/forum/threads/vw-polo-running-problems.164490/

do you have a code reader?

Thanks for the replies chaps, all good ideas to try.

I'll try the new plugs and coils, if that doesn't work I'll order a compression tester and go from there. Thanks for offer of help Steve, will be ok I reckon unless it all goes tits up and I split a plug etc.

If it's timing chain or a new head I'll probably have to scrap it. It's got 105k on it and probably only worth 500 quid or 300px.

No worries.

I have got a bluetooth code reader somewhere in the garage if you decide you need one though they're peanuts on the net these days.

Shout if you need help.

Steve

Compression testers aren't that expensive IIRC - no harm in having one either.

The coils are a common failure but are usually linked to the plug condition, if you replace the plugs and coils and it runs fine from cold to operating temperature everything is a-ok.
If there was a lot of ash fouling on the plug ceramic, it's likely there is a mechanical issue, if you have an obd code reader that does mode $06 misfire counters, it will show up misfires that are not percieveable at idle (due to compression issues)

On the mechanicals, the valve guides wear badly on the exhaust side, low compression and intermittent poor running are both symptoms. This also causes the seat to oval and the valve to pit/burn.
I always get all the exhaust guides and valves replaced, and seats recut as required.
I have repaired several with 20-30k miles that have been worn like a 300k miles engine, the higher mileage vehicles seem to wear better - i don't know whether that's coincidence or short below operating temp journeys causing accelerated wear.

I also have had injector failures on these - a stethascope will isolate which one is not working by the sound of the click as it operates - you may get fault codes depending upon how the injector has failed.

On the vehicle value, the only viable repair would be an injector, i would be certain that there are no mechanical problems before going ahead with any repairs.
If there is a mechanical fault, replacing the coils and plugs may make the engine run acceptably(but not 100%), but ensure the catalyst is not being overheated (from unburned fuel due to misfire) as it is close enough to the undertray to catch it on fire!

Dave

Hi Jon,

I had a similar problem with a 1.2 6V engine - these engines are a total nightmare as you have probably gathered from the internet.

The main issue I had was a burnt exhaust valve on cylinder 3 and severely worn valve guides. I ended up going through all the usual things of coil packs, plugs, timing chain etc. etc., however the remedy to get it running properly and through an MOT was a new set of valves, valve guides and a set of piston rings.

If you are thinking of tackling it I have a 9N Haynes manual you are welcome to have- just U2U me. You'll also need the timing tools if you take the head off - I have these as part of a larger set so if you are going to go for it U2U me and we can sort something out.

Alternatively sell it as a non runner - I just persevered for the challenge, it certainly wasn't an economical or quick fix.

So looks like the coil and plus replacement worked. Seems to be running fine again. New coils were a pain to fit, one connector broke unplugging them. I guess after 12 years they were a little brittle. I also used wood and a lump hammer to get the new ones to sit right down on the plugs. Probably not the VW way but it worked!

Thanks for all the tips.

Jon

Result. Well done.
Steve

Who says the Germans don't have a senso of humour? If only everything in life was as reliable as a Volkswagen!