Another thread about a misfire on cylinder 2 (1.4 AUA engine)

My gut feeling is it could easily be a coil problem. I have just purchased a "kosher" one from those nice people in Crewe. Cheapo electrical bits are never a very good idea.

Comments re Gary seconded, he's terrific.

My missfire is very minor, and intermittent. So step one: a decent coil pack. Step two: ask Gary when he replaces my clutch.

Good luck.
 
simon martyn said:
My gut feeling is it could easily be a coil problem. I have just purchased a "kosher" one from those nice people in Crewe. Cheapo electrical bits are never a very good idea.

Comments re Gary seconded, he's terrific.

My missfire is very minor, and intermittent. So step one: a decent coil pack. Step two: ask Gary when he replaces my clutch.

Good luck.
Click to expand...

It highly unlikely as it’s a shared spark you could swap round on the coil, I can’t remember which are shaded but I think it vertically on the coil.

I’ve had this issue and changed so many things, but in the end it was a valve


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Hi all,

Thought I should probably do another update on this, as things have improved.

About a week ago I decided I would do an oil flush, as there was a lot of black gunk visible through the oil filler.

I used a can of oil system cleaner and ran the engine as per the instructions. I then drained it (no filter change), and refilled with a menage of random engine oils - ends of cans from other oil changes - and ran the engine for just a minute or so as a sort of rinse, to minimise the amount of the cleaning product left in the engine. I then let that drain, with the car raised up at the front, for about 6 hours. I also removed the old filter at this point. I then refilled with some nice fresh oil of the correct spec.

Getting back to the misfire, next I cleared all fault codes and tried swapping the leads between cylinders 1 & 2 again, and immediately noticed a spark jumping from lead 1 (previously lead 2) to the cam cover.

Was delighted to have found the issue, and so let the engine tick over again until the misfire started. Stopped the engine and read the fault code only to discover that the misfire was STILL on cylinder 2. Not sure how that could be, given that lead 1 was definitely arcing out, but still, it was an excuse to go back to Euro Car Parts and get the leads replaced.

In the meantime the can of 'Wynn's Hydraulic Lifter Treatment' I'd ordered arrived (on another thread a someone reported curing a similar issue with that), so I swapped out the leads and poured that into the engine too. And I haven't managed to trigger the misfire since.

I'm not sure I trust that it's totally sorted yet, and I don't know if it was the leads or something gunged up in the head that was the problem, but it's certainly better. I do also have a new coil pack in the post, so I will swap that out too just to see if it makes any difference. Can always keep the old one in the car as a spare.

And after adding that stuff it's a bit quieter, too. It now only sounds like one 1980s Ford diesel with some loose nuts in the crankcase, as supposed to sounding like two of them. Progress, of a sort! ?

I do worry a bit that it seems so damn noisy - it makes the 2 litre SR20 in my other car sound like a well-oiled sewing machine. But I suspect until I can make it to one of the Bristol get-togethers and hear another 1.4 petrol for comparison, I can't really judge if it's an issue. Anyway, thanks to everyone for the help and advice.
 
Few I worked on sounds alright, though I don't have that much experience with petrol, the 1.6 FSI I recently acquired does sound fairly smooth after bolting an exhaust back on it, though it does have a slight rattle with bonnet on and things buttoned up it is really quiet, especially compared to my 1.4tdi.

What I had with my 2.0 TDI when turbo was going, oil in intake dissolved a bunch of gunk build up, after 2 weeks of trying to figure out why it had white smoke it just stopped with nothing done, I can only assume it was the carbon/oil mixture keeping one or more valves from closing fully causing it to have incomplete combustion, exactly as bent valve on my A2 however it would keep running fine.

It might be unrelated, however a good bit of abuse might just sort it, especially with intake etc. being cleaned not too long ago, it could also be that.

Happy to hear you're making good progress with the little 1.4 after all the struggles!
 
Well done on you Martin, your perseverance seems to be paying off!

A Bristol meet……


Sent from the future
 
mowog said:
Hi all,

Thought I should probably do another update on this, as things have improved.

About a week ago I decided I would do an oil flush, as there was a lot of black gunk visible through the oil filler.

I used a can of oil system cleaner and ran the engine as per the instructions. I then drained it (no filter change), and refilled with a menage of random engine oils - ends of cans from other oil changes - and ran the engine for just a minute or so as a sort of rinse, to minimise the amount of the cleaning product left in the engine. I then let that drain, with the car raised up at the front, for about 6 hours. I also removed the old filter at this point. I then refilled with some nice fresh oil of the correct spec.

Getting back to the misfire, next I cleared all fault codes and tried swapping the leads between cylinders 1 & 2 again, and immediately noticed a spark jumping from lead 1 (previously lead 2) to the cam cover.

Was delighted to have found the issue, and so let the engine tick over again until the misfire started. Stopped the engine and read the fault code only to discover that the misfire was STILL on cylinder 2. Not sure how that could be, given that lead 1 was definitely arcing out, but still, it was an excuse to go back to Euro Car Parts and get the leads replaced.

In the meantime the can of 'Wynn's Hydraulic Lifter Treatment' I'd ordered arrived (on another thread a someone reported curing a similar issue with that), so I swapped out the leads and poured that into the engine too. And I haven't managed to trigger the misfire since.

I'm not sure I trust that it's totally sorted yet, and I don't know if it was the leads or something gunged up in the head that was the problem, but it's certainly better. I do also have a new coil pack in the post, so I will swap that out too just to see if it makes any difference. Can always keep the old one in the car as a spare.

And after adding that stuff it's a bit quieter, too. It now only sounds like one 1980s Ford diesel with some loose nuts in the crankcase, as supposed to sounding like two of them. Progress, of a sort! ?

I do worry a bit that it seems so damn noisy - it makes the 2 litre SR20 in my other car sound like a well-oiled sewing machine. But I suspect until I can make it to one of the Bristol get-togethers and hear another 1.4 petrol for comparison, I can't really judge if it's an issue. Anyway, thanks to everyone for the help and advice.
Click to expand...
Did this resolve the issue? I’ve just acquired a 2000 1.4i with a very similar issue, only this time on cylinder 3 (assuming we’re calling the free end of the engine cylinder 1!!).

Only difference is that she missing straight from the get go, but clears as soon as you bring the revs up. Strong spark, good leads & plugs etc, tried swapping around to no avail so on and so forth. Going to do an engine flush then get some new oil and treatment in and see what happens!

Nick
 
Hi Nick,

So I think my misfire was the collective result of a number of things, plus the distraction of a brand new plug lead that was failing.

The engine flush and additive definitely made a difference, as did the new coil pack. In the months since doing those jobs the same engine code has been triggered once more, and I put that down to the wear in the top of the engine.

My MOT tester (who is a clever chap) said as much - apparently the AUA engine tends to suffer from oil starvation to the valves and cams when the strainer gets clogged in the sump. Perhaps more surprising is that it doesn't effect emissions, at least not from an MOT point of view.

So yes, the slightly shorter answer is that if I acquired another 1.4 petrol VW/Audi with a misfire, I would swap (in order), plugs, leads and coil pack, and do a proper engine flush. Beyond that I think you're looking at wiring, a faulty injector (though maybe that's a different code?), or ECU.

Hope you get it sorted!

Cheers,
Martin
 
mowog said:
Hi Nick,

So I think my misfire was the collective result of a number of things, plus the distraction of a brand new plug lead that was failing.

The engine flush and additive definitely made a difference, as did the new coil pack. In the months since doing those jobs the same engine code has been triggered once more, and I put that down to the wear in the top of the engine.

My MOT tester (who is a clever chap) said as much - apparently the AUA engine tends to suffer from oil starvation to the valves and cams when the strainer gets clogged in the sump. Perhaps more surprising is that it doesn't effect emissions, at least not from an MOT point of view.

So yes, the slightly shorter answer is that if I acquired another 1.4 petrol VW/Audi with a misfire, I would swap (in order), plugs, leads and coil pack, and do a proper engine flush. Beyond that I think you're looking at wiring, a faulty injector (though maybe that's a different code?), or ECU.

Hope you get it sorted!

Cheers,
Martin
Click to expand...
Cheers Martin,

That’ll be the order less the flush as it’s due anyway. I’ll let you know if the flush helps solve.

Nick
 
mowog said:
Hi all,

Apologies if this is poor form, as I've already mentioned this issue on another thread. I just wanted to create one specific to this problem in the hopes that someone reading/searching has more of a clue than me. This seems to be a regularly occurring fault with the AUA engine, as there are numerous mentions across the web.

The issue is as follows: the engine starts and idles OK, but if I leave it idling for a few minutes it starts to misfire on cylinder 2.
  • I know it's happening on number 2 because if I remove the plug lead or injector connection there is no change.
  • There is a strong spark being delivered - it shoots out of the lead when I unplug it. This makes me think the issue is not the coil pack.
  • Swapping over plug and leads from cylinder 1 makes no difference - the fault stays on 2. This suggests that the plug and lead are fine.
  • No fault codes are being raised (which seems really odd to me).
  • When I rev the engine it sounds/feels like the misfire goes away.
Having read this thread, I tried swapping out the knock sensor, but to no avail. In recent days I've also replaced the MAP sensor, cleaned the throttle body and EGR valve, and checked for air leaks.

The fact that the engine has to idle for some time before the fault occurs is curious, and suggests that the issue is related to the engine warming up.

Has anyone ever heard of a fuel injector that stops working when warm? I haven't, and I'll be honest that it seems unlikely to me. Is it easy to swap injectors over to test if that is the culprit? I've never tried.

As I say, this exact issue seems to be not uncommon, and I'm sure someone must have worked out what the issue is by now. What I'm struggling with is the fact that it only effects the one cylinder, and only when left idling for a while.
Click to expand...
Hiya, I have this problem on my BBY…the ecu counts the misfires then cuts off the fuel injector to that cylinder to avoid damage to the catalyser..when it misfires switch the engine off for a minute then restart…any help??
 
This is standard behaviour of the ecu to count misfires. When it reaches 400 it cuts the fuel to the injector to protect the CAT

I chased this very same fault on an AUA engine for weeks
From cold it ran on 4 cylinders perfectly as it warmed up it would drop on to three
Vcds always stated it was no 2 cylinder
Changed knock sensor map sensor clean throttle body and readapted it same with egr. Nothing made any difference
Changed plugs as well
Checked plug leads all seemed fine

Then on a quite night in the garage as it was still running on four cylinders I heard the tick tick tick of a hit lead sparking to earth then it dropped on to three cylinders.
Took of plug lead No2 and have it a really really good examination under a good magnifying glass and pulled the rubber around and then I saw it. A bloody tiny hole in the rubber just at the point where the hard section transitions into the soft section

I could not get a plug lead quickly so I degreased it and ran a tiny bit of thin super glue onto the hole then put a piece of heat shrink tubing Over the effected area
Problem as never reoccurred to this day and that was all about 2018

Paul


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I would still say this is a sticky/broken valve as mentioned earlier in the thread. A compression test will confirm.
We had to fit a recon head and the suspect valve could be clearly seen as there was actually a tiny piece missing causing non compression. Ours ran fine, even with the broken valve, when cold, then got worse once hot. No codes were showing.

Ian
 
Kleynie said:
I would still say this is a sticky/broken valve as mentioned earlier in the thread. A compression test will confirm.
We had to fit a recon head and the suspect valve could be clearly seen as there was actually a tiny piece missing causing non compression. Ours ran fine, even with the broken valve, when cold, then got worse once hot. No codes were showing.

Ian
Click to expand...

Good call Ian I should have mentioned on mine I ran a compression test and all 4 cylinders where within 10psi of each other which is well within spec
I also double checked timing belt for correct fitment etc

I would appear that these AUA BBY engines are prone to sticking valves, not sure if this is a design flaw or the result of iffy servicing

Paul


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Even if the leads and coil on an AUA look o.k - it is worth taking the coil off and having a look at the underside and back of the casing - on ours there were small stress cracks on the underside adjacent to where the screws clamp it to the engine block and the potting compound on the back of the unit was perished / coming away from the edges of the casing. The coil consequently was able to earth to the block randomly. As most of these if still original are the thick end of 20 years old, exposed to heat and vibration, it is not surprising that eventually the insulation succumbs to wear and tear. After a false start with an Amazon overnight delivery coil that worked for about 5 minutes and then lost one output completely (but still ran a lot better than a knackered original), a Bosch one solved the issue completely.
 
I would be stripping the loom back off each coil plug back to the main junction. I found open wires that were corroding I put heat shrink tubes over them to shrink them and the problem was solved.
 
Thought I’d give an update as to how mines progressing.

Today I added some wynns engine flush and ran the engine up until it was hot, then left it idling for 20mins. The misfire could be heard clearly through the exhaust. Slowly but surely, the misfire began to clear.

I drained out the oil, changed the filter then filled with fresh oil and wynns hydraulic lifter treatment.

I can confirm that the misfire is all but gone (the occasional hiccup) and the eml has gone off, so sticky valves are certainly an issue on the AUA engine (unless somebody has a better explanation?)

Iffy servicing is most certainly a culprit on this A2, as is the car sitting for 2 years (to the point where the engine was frozen and needed lots of wd40 and a breaker bar to turn over).
 
depronman said:
Almost certainly a sticky valve
I chased a mis fire on an AUA engine for hours
Would start from cold on 4 cylinders then drop onto 3 and it was always number 2 that was cut
The ecu monitors the number of misfires and using the knock sensor works out the offending cylinder and then cuts the power to the injector to protect the cat but his also throws an engine mil light. Cycling the ignition would clear the fault and it would run on 4 cylinders for a min or so then drop back to 3
But the mil light would be on until cleared with vcds
On my AUA it was eventually traced to a faulty plug lead I actually heard it arcing just before it dropped on to 3 cylinders

However the far for common issue is a stuck valve and this does not cause a mil light or any fault codes and commonly only occurs when the engine is warm and nearly always affect cylinder 2 but can affect other cylinders
Another cause is a slightly bent valve normally after a cam belt breakage
Worth looking at the long and short term fuel trims as they tell the story of what is going on
That engine is very susceptible to air leaks and the ecu is easily confused into shutting down a cylinder to protect the cat

Paul


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Click to expand...
Paul , after our recent conversation and reading Mowog,s problem, it looks like I’ve got same problem, everything he describes fits mine to a T, with the exception of mine not lighting up any eml lights, would a compression test give it a definitive verdict do you think,
 
Paul further to my last message, should the compression test show no loss, is it possible to introduce a oil additive as a persuader to the sticky valve/s.
 
I did a compression test on mine but it was all rather inconclusive. I suspect the starter doesn’t turn the engine over quickly enough for the sticky valve to show up and also the engine is cooling down all the time you are fitting the compression tester

I didn’t find any oil additive that was guaranteed to work
The only real cure is to wip the head off and sort out the problem with the valves once and for all


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