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Part 1 - the problem:

Long story short: it started as a mis-fire, then turned into running on only 2 cylinders. 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.

I've done a compression test: 1 2 3 4
175 125 155 155

Having bad thoughts now of it being a head gasket (it's always consumed a tiny, tiny amount of coolant) or something internal having failed/worn. I think I've read something about valves failing on these? Any ideas any one?


Part 2 - what to do:

I want to sell it anyway and get a new project, but I'm wondering if it's worth fixing the car, which I'll have to pay for as uni has just started and I've got a final year dissertation to do (joy!), or braking it, which seems a shame as otherwise it's a nice example in pretty decent condition all round. I'd expect a head gasket to be about £5-600 to replace, which makes the car worth about £1-£1.4k max to me once sold. Or do I just try and swap the engine for a known, working GTI engine and ask a friend to do the swap for me.

The final option I'm thinking of, which my dad suggested based on previous plans, is to try and do a cheap 1.8t conversion (wondering what the cheapest it could be done for is), then sell it on for a (hopefully) profitable sum after a couple of months/in the summer for show season. I'm sort of drawn to this, as I know someone who could do the work cheaply, or in exchange for stuff I've done for him on various computers, and I wanted to do it anyway. Not sure what the going rate for a converted one is, but I'm guessing £5k ish?

Just after people's thoughts on this, try and see what the general consensus is, but to me they all look pretty dim financially!

do you have water in the oil ?
do you have oil in the water?
if you start it with the water expansion tank cap off does the water come out of the tank or see bubbles?

if no to these do compression test again, then put a bit oil down plug hole and test again, if the reading shoots up, rings have gone, if it stays the same valves.

Awesome, will try those and see what happens. Will be Wednesday before I get a chance though, but will report back.

Thanks!

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

Just found an ECU on eBay for £5 + postage, so will try that and see how it goes. I think I've got a friend who can code it in for me too. I doubt it'll make a difference, but for £15 it's worth a shot IMO. Can always sell it on again after if it's not any better.

Stupid question probably but have you vag comed it?

Cracked plugs wont fire under compression, also when you remove the plugs from the cylinders missing are they wet with petrol, if wet petrol getting there, try swapping the plugs from the working pots with the non working pots. on the slight coolant use, bang in a bottle of K seal, it works a treat. does the engine sound very tappety when running. and never assume because something is new that it works.

if plugs in 2 and 4 wet, swap plug leads over at coilpack

Outside shot but here goes...

You've established you have injection and sparks on all 4 BUT in the right order?? It could be all out of sync due to a faulty crank or cam sensor. Without these you have no timing. The cam sensor is prone to playing up too. It's a long shot but could also be a simple fix. HTH

benmkiv wrote:Stupid question probably but have you vag comed it?

Yeah. It just said 'multiple misfires found'. Useful!

Didn't sound tapety or bad, just missing. My dad posted something like this Club Polo which you, GeorgeN, replied too. We tried that, and it's back to normal again! Swapping the leads for 2 + 4 at the coil end fixed it.

I feel like a massive retard, but genuinally don't know how/when the leads got mixed up. Regardless, it's working now, and I'm truly grateful for your suggestion!

We had also swapped the plugs all around before now - both the new and old ones and it made no difference.

Stan, I was thinking of something like that, but happily it was a much cheaper fix!

TriggerFish wrote:

benmkiv wrote:Stupid question probably but have you vag comed it?

Yeah. It just said 'multiple misfires found'. Useful!

Didn't sound tapety or bad, just missing. My dad posted something like this Club Polo which you, GeorgeN, replied too. We tried that, and it's back to normal again! Swapping the leads for 2 + 4 at the coil end fixed it.

I feel like a massive retard, but genuinally don't know how/when the leads got mixed up. Regardless, it's working now, and I'm truly grateful for your suggestion!

We had also swapped the plugs all around before now - both the new and old ones and it made no difference.

Stan, I was thinking of something like that, but happily it was a much cheaper fix!

Glad its sorted mate

Same! Again, thanks!

And off to Autotrader it goes!