Hi all,

To start, car is a 6n2 Polo GTi (1.6 ARC engine) and has been faultless until now. Now though it only works on two cylinders. Anyway, here's what I've done/tried so far. If anyone has any suggestions at all, I'd love to hear them! Sorry to copy/paste from another forum, but the Polo forums are either a) quite quiet or b ) full of "look at ow low ive made me 1.0 polo. its got strecht n verythin. i then beat a ctr cos ive got more areodynamics" type people. That said, there are very knowledgeable people on there, but they are the minority sadly.

Long story short: it started as a mis-fire, then turned into running on only 2 cylinders pretty much over night. Had new spark plugs, no change. Tried the old (but working, just cracked casing) coil, no change. New leads, slight improvement, still got the same issue though.

If you unplug injectors 2 & 4, it still runs rough (it runs just the same on 1 & 3 as it does with all 4 plugged in). Unplug either 1 or 3, it stalls. Checked output from the injector plug terminals - all 4 have equal voltages/pulses. Leaves only the injectors then, surely? Nope. 4 new injectors/fuel rail and it has the exact same symptoms.

At the moment it runs, but I can only just get above 40mph, and I'm not even at 30 by the end of my road (I'd guess I could get up to 50ish if it were working properly).

Part 2

Right, tried several more things on this over the past weeks.

In summary:

As suggested above, water is flowing around the system properly. Oil/water all separate.

Different leads, plugs, coils and injectors.

Removed injector rail from engine and cranked it over - all 4 injectors are working (meaning I've got 4 spare injectors too now! -_-).

All plugs are getting a spark (although on one of the coils tested plug 2 doesn't spark as fast as the others do).

Does anyone know if it's a wasted spark system on these engines?

Compression tests read 150 on all cylinders, from cold with throttle open.

Dropping oil in makes no difference.

Cylinders 2 & 4 aren't working properly. We can remove the leads from the plugs and the engine runs the same. We can then remove the plug off of cylinder 1 as well (so with just cylinder 3 working) and the engine runs (until returning to idle) on just one cylinder.

With the injectors on cylinders 2 and 4 unplugged, on the overrun nothing happens. With them plugged in, the exhaust pops and bangs, so fuel is getting injected, but not burnt. Which is odd, as there is a spark there!

We're fresh out of ideas here. There's no bad mechanical noises and it pretty much came on over night. It's always missed a little from cold, but blipping the throttle has sorted it. This time it worked one day, then didn't the next. I'm wondering if somehow it's the ECU making it not work properly? All VAGCOM says is 'misfires on 2 and 4 found'. Really, really useful! At £30ish I'm half tempted to buy one to test, but I think it'll need coding in, which I can't do.

I'm looking to sell (or torch!) this, but would rather either a) fix it, or b ) diagnose it so both the seller and I can get a fairer price.

Thanks for any input!

Joe

Oh, guess it's worth adding that these have one coil for all 4 cylinders, unlike the coil-per-cylinder system on the 1.8t's. You can't get the head off without un-timing them/dropping the engines due to the fantastic way VAG designed the heat to hold the cam system so this a last resort.

Cheers!

Edited 17 November, 201213 yr by TriggerFish

I think Teflon Tom knows this engine quite well. I could be mad, but get the impression he dropped one in a felicia.

Probably worth an ask.

Good thinking - he posts on the Polo forums too thiking about it.

Cheers.

Edit - to update this, it's now working!

Had the suggestion online of swapping the leads at the coil on the dead cylinders, which fixed it. To say I'm happy is an understatement, to say I feel like a retard is also an understatement!

Edited 18 November, 201213 yr by TriggerFish

i have vac com if that helps and can read codes sounds to me like ecu problem

Edited 19 November, 201213 yr by uma1998

You've got a reply PM. Thanks for the offer, but I've managed to fix it now and have VAGCOM myself.

Like a complete moron, I'd wired the coil up the wrong way round at some point. I fitted new leads to try and solve a misfire, so I guess it all got hidden in the same type of symptom.

Regardless, thanks for the thought!

You've got a reply PM. Thanks for the offer, but I've managed to fix it now and have VAGCOM myself.

Like a complete moron, I'd wired the coil up the wrong way round at some point. I fitted new leads to try and solve a misfire, so I guess it all got hidden in the same type of symptom.

Regardless, thanks for the thought!

Woo, oops

Never mind at least it was a cheapish doh moment.

I'm surpirsed it even ran with the coils on the wrong way.

Glad you got it sorted.

Phil

Only two were backwards. Although when troubleshooting I had it with only 1 plugged it and it was running! It would rev up from idle (around 4-5k I went too), but couldn't return to idle without stalling.

I'm glad I've got it sorted too - got an interested buyer already.