2nd Opinion Please

Chat about your 9n Polo (inc GT and Fun)
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rogerowen
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Drives: 2003 VW Polo 1.2
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2nd Opinion Please

Post by rogerowen »

My daughters recently acquired 2003 Polo 1.2 has started chugging. If it were a 4 cylinder car - it would feel like it's running on 3! So, after realising that it's a 3 cylinder engine......... running on 2.

First check was for spark - all 3 OK.

2nd check was compression - Cylinders 1 and 3 have 220 psi, but Numbers 2 only makes it to 180 psi.

Spark plugs 1 and 2 are dry and sooty. number one plug is wet with petrol.

There is no misfiring, just regular chugging and poor performance.

I'm thinking head gasket failure, or burnt valve in No 2.

Water is clean and oil is not emulsifying.

ANY THOUGHTS Please? I'm about to launch into a head off rebuild unless anyone knows of another test to carry out. THANKS.
rogerowen
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Re: 2nd Opinion Please

Post by rogerowen »

Sorry - Plugs 1 and 3 are dry and sooty. Plug number 2 is wet. :oops:
RUM4MO
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Re: 2nd Opinion Please

Post by RUM4MO »

You are sure that cylinder 2's coil is firing okay - is the engine malfunction on? (I'm guessing not)

Next move might be to swop the injectors between 2 and another cylinder to see if the wet spark moves with the injector.

Obviously swopping coils first to see if the wet spark plug moves, but it sounds more like an injector fault - but that is just a guess!
rogerowen
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Re: 2nd Opinion Please

Post by rogerowen »

Umm, the possibility of an injector fault has actually been bugging me, would be a lot easier to fix than an engine top strip down! Thanks for the tip - I'll give that a try. Orange engine light came on some time ago, solid at first - but now is flashing. EPC light also came on so I uncliped the throttle body sensor (seemed clean), replaced it and the EPC light went out. Thanks again, will repost any news in the hope that it might help others with the same quandre.
rogerowen
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Re: 2nd Opinion Please

Post by rogerowen »

Just taken out the wet plug from No 2 cylinder again - not petrol - oil!
rogerowen
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Re: 2nd Opinion Please

Post by rogerowen »

Checked spark again on No 2 after cleaning the oil off it. Good Spark, refit and run - engine still chugs. Removing coil lead while running makes no difference.
RUM4MO
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Re: 2nd Opinion Please

Post by RUM4MO »

rogerowen wrote: Mon Jun 18, 2018 4:20 pm Checked spark again on No 2 after cleaning the oil off it. Good Spark, refit and run - engine still chugs. Removing coil lead while running makes no difference.
Right, this might be a cable harness issue, I've never ever had a 1.2 3 cylinder petrol engine, but, something in the deepest dullest bits of my memory does think that I've read a bit about this. Where exactly in the harness the problem normally is I can't say - but I think that it is along the top of the engine somewhere.

Maybe start attacking Google with suitable phrases concerning that - ie coil harness issues on a 1.2 3 cylinder VW engine - plus any other phrases that seem suitable.

Edit:- I'd hope that the oil on the plug is just due to the engine being run without that cylinder firing.

Another Edit:- have you tried using "search" on this forum, and on briskoda.net and on seatcupra.net - if I'm correct on potential coil harness issues, then I'd expect one of these 3 forums to have reported it already as they all used these engines.
rogerowen
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Re: 2nd Opinion Please

Post by rogerowen »

Thanks, that might be worth a look in terms of wiring to the injector.
rogerowen
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Re: 2nd Opinion Please

Post by rogerowen »

Latest..... Just removed the injectors and all are working.

So, to recap there's spark and fuel going to each cylinder. Slightly less compression on No 2, 180 psi as opposed to 220 on No 1 and No 3. And - No 2 plug is oiling.

No 2 is as dead as a Dodo, no misfire - just nothing.

Compression is holding - which might rule out piston hole, broken piston ring, burnt out valve.

My dear Watson! No fuel can be entering the chamber? Which means that the inlet valve isn't......?

Theory at this moment is that either the fuel and spark at No 2 is not happening at the right time, but surely this would be accompanied by misfire/backfire?

Or, somehow inlet valve is stuck in the closed position.

I could limp in to somewhere for a 'diagnostic' - but I'm not convinced this will expand much on what I've already discovered by trial and error. Happy to be told differently by anyone with better knowledge.

Next step looks like head off to me. :shock:
rogerowen
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Re: 2nd Opinion Please

Post by rogerowen »

Drats! Unhooked electric supply to the fuel pump so I could look down the injector hole while cranking (and not get soaked with petrol from the injectors) ......and, the inlet valve is working perfectly!

Now completely at a loss to fathom what could be wrong. :(
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