Mk7 Golf 1.4 CMBA fouling plug - uuugh boy. [Modern content]

[edwagon]

I've got a mk7 VW Golf here which I'm trying to get running as a daily driver.
It's a 2013 with the CMBA engine - 90kw.

It was running on 3 cylinders when I got it. Dead miss on #2. Switched coils around, miss stayed with #2.
Pulled plugs, worst I've ever seen, worn down to the insulators - couldn't believe it!

Ran beautifully with a new set of plugs and a clean up of coils etc.

But 20km later it dropped a cylinder - #2 again. Had to nurse it 5km home, pulled plugs, all looked a bit wet but #2 the worst.
Quick squirt of brake clean and compressed air and its back up on all 4 again and feeling strong.
I changed the oil and filter and took it for a good drive up the motorway with plenty of load and rpms in bursts. Drove perfectly. 
The next day it was back on 3 cylinders after 2x short trips from cold.

I've just got home from repeating the fouled-plug cycle for a third time - always #2, plug always slightly wet and always come right with a squirt of solvent.
It is hard to say for sure if it's fuel or oil fouled, I've always had to drive it a few km before I can pull them to check and so they're BOTH fuel and oil fouled by the time I can check.

It is not breathing heavily and apart from fouling the plug, seems to run really well.

I know VAGs of this era are known to burn oil. I haven't driven this far enough to gauge if its burning oil. Possibly a puff of smoke but it's not conclusive. Back of car is sooty though.

Do I have an oil control ring on #2 that is so weak the plug fouls that quickly?
Or a crook injector?
Or anything else to check? PCV valve?

[Rich]

It Broken. Paging stealthstylz to the ‘sorry here is some bad news’ phone.

[stealthstylz]

Aug 6, 2023 8:50:45 GMT Rich said:

It Broken. Paging stealthstylz to the ‘sorry here is some bad news’ phone.

LOL. I read it first thing this morning and was trying to think of a tactful way to say it's knackered, or positive ways to sort the issue that aren't expensive, but I can't think of any. Literally best I can come up with is clean it all up again, trailer it to the auctions and hope the fault doesn't pop up whilst it's driving onto the block.

The 2nd least expensive option is to buy/fit a low mileage engine with scrapyard warranty then sell the car.

The most expensive and only way to fix it properly option is to pull the engine, strip it and de-glaze the bores, fit new rings and have the head reconditioned (valve guides are always toast on VW's if they've done more than 1000 miles), then bolt it back together with a new cambelt etc and sell it as a super well maintained version and hope you get most of the money back.

The common theme of all these options is that you should sell it and buy something that hasn't got a VW That's F**king S**t Innit engine.

[automax]

If you're unsure if it's fuel or oil fouling the plug, swap the injector from the offending cylinder with say cylinder 4. If it fouls again but this time its cylinder 4 with the injector in it from cylinder 2, you know its an injector issue. if its still cylinder 2, you most likely have a ring problem (ooo'er).

[edwagon]

Thanks for your replies fellas.

I bought it for scrap value on the basis that the engine was a goner, so no need for sugarcoating.

I'm just surprised how quickly that plug fouls given how clean the engine is and how well it runs.

automax lol @ ring problem.

stealthstylz do these things normally come right with the new revised pistons, rings and a set of guides?
Are they ok to work on once you get into them?

I'm totally willing to rip it's head and pants off and give it a birthday if there's a reasonable chance it'll be a good runner for a couple of years. It's had the DSG done recently and it seems to be a good little car apart from this.

However if I'm just chasing unicorns with the CMBA and it's too risky/will never be right then I'll kick it to the kerb instead.

[stealthstylz]

I've never had to do one again, and we still MOT a couple that I did 4 or 5 years ago that are still running good, and have done more miles then they had when they first broke. They're pretty easy to work on. I do recommend that people thrash the absolute balls out of them for at least 20 minutes, at least once a week though.

[kevins]

see if you can find some hotter plugs? potential for them to melt but doesn't sound like you have much to lose.

[edwagon]

Update on this - I have had it running nicely for the past 6 weeks.
Two things seem to have helped:
1. Drove it in daylight and realised that it wasn't smoking under load at all, but smoking pretty dramatically when accelerating after a downhill run. So the stem seals are toast, and possibly the guides as above. Lesson: keep the rpms down and give it a strategic squirt of throttle on downhills (it's quite hilly in our area). This is the opposite of how I had been driving it previously, with plenty of rpms and engine braking.
2. Gapped the plugs down slightly, from 1.1 to 0.8.

With a bit of driving technique and gapped plugs it has been as a good as gold for 1000+km, and used a mere liter of oil.

I'll still address it properly but at least this gives me a bit of breathing space.