Polo 9N3 Engine Management Light

[DJPT-UK]

I have a 2005 Volkswagen Polo 1.2 (55PS) E.

Yesterday I pulled up at home and was stationary with the engine running for about two minutes. I noticed the engine started juddering and felt lumpy, then the engine management light was flashing. The engine would only just rev and it felt like it was on reduced power or something. When I switched the engine off and immediately back on, the light had gone off and the engine was running fine!

Bizarrely, I drove the car to work this morning (about ten miles away) and it was fine, but the same thing happened when I got it home again tonight. When I'm driving it's alright, there's no loss of power or warning light. I'm taking it to a local garage on Wednesday so they can see what the fault code is.

Just after a heads up really, any ideas what it could be? Surely it can't be anything serious because it seems pretty intermittent, and only happens when the engine idles for a few minutes - but not all the time. I've checked the brake lights too because I read that sometimes that can cause the engine management light to come on.

To be fair it's been an excellent car - done 107,000 miles in it from new and it has never ever cost me any money or let me down!

Thanks in advance

[DJPT-UK]

So, the mechanic has had the car on VAG-COM which has confirmed the engine is mis-firing when the engine management light flashes.

I have had all three coils replaced and still the problem remains. I had to wait a couple of days for the parts to come in, but as luck would have it, it ran fine during the wait! The mechanic did reset the warning light when he had it on VAG-COM and it did not come back on while I was waiting for the new coils.

The mechanic says it could be a dodgy spark plug, and when you have coils replaced ideally you replace the spark plugs too? It is bizarre because the fault happens intermittently (usually when the engine idles for a minute or two), and when I stop and re-start the engine it is fine.

Any ideas what the problem could be before I spend any more money?

[perky85]

If you have had the coils replaced, then replace the spark plugs, while the plugs are out it wont hurst to do a compression test.

Also chech the throttle body may need cleaning & re-adapting

[DJPT-UK]

Thanks Perky.

Since I posted originally, I have had the spark plugs replaced and the problem still remains. The engine idles at around 700 RPM (constant), is this about right?

I am taking it to an independent VW specialist on Wednesday who are going to do a compression test.

[Crasher]

Exhaust valve failure, this is becoming extremely common on the 1.2 3 cylinder engine, I can hardly get one rebuilt before the next one comes in.

[DJPT-UK]

If it was the exhaust valve, wouldn't the engine run like crap when I'm driving? How much money am I looking at if that is the problem?

I'm actually dreading the compression test tomorrow...gulp

[Crasher]

The 3 cylinder engines react very sensitively to a drop in compression, any more than a drop of around 2 bar to another cylinder will start to make them run rough, if the compression drops too far, the ECU detects the difference in speed of the crank rotation and using the camshaft position sensor it can calculate which cylinder is loosing power and starting to misfire, it will then store a code or two such as "cylinder 1 misfire detected" and "random multiple misfire" and turn off the injector to that cylinder to prevent damage to the delicate catalytic converter and to avoid excessive tailpipe emissions, this system is part of the EU4 emissions protocol. Before it reaches this stage, the intermittent misfires can be observed in Measuring Blocks 08 using a diagnostic system such as VCDS. The 6 valve (BMD 54PS engine) 2005 Polo we did last week had 35K on the clock and had a burnt out exhaust valve on number 1. We rebuilt the head and also fitted a full timing chain rebuild kit and this cost the lady £1250.

[DJPT-UK]

Crikey, I hope it isn't the exhaust valve then!

Is it at all possible it could be a dodgy sensor somewhere maybe? It tends to mis-fire when the engine is at normal operating temperature, so usually when I've driven home from work. The engine light came on last night, but it wasn't on this morning when I drove the car to work.

I'll post on here tomorrow after the independent VW specialist has had a look.

[DJPT-UK]

So, IVC Leeds did a compression test today and confirmed the exhaust valve on cylinder three is causing the problems.

They have quoted £800 for it to be repaired but I'm looking around for quotes before I get anything done.

On a positive note, I've been lucky because apparently some engines don't even make 50,000 miles before they get problems and mine has done 107,000!

[perky85]

glad you got to the bottom of this.

Its not what you want at this time of year though