Refurbishing an AUA

[Robin_Cox]

So. After I wrote the post above following fitting the new (Amazon) coil and an idle / fast idle test, price (!) came before a fall. Next time I went to start up it was back on 3 again - but it was a new error I've never seen before. Ignition for cylinder 1, open to earth. Reset, switched off and on again, cleared faults, no change. The new cheap coil had failed on one output even though the other cylinders that had previously been problematic were now running smoothly. Luckily Amazon took it back in 24 hours with a Royal Mail special delivery print-out label and refunded a couple of days ago, and I ordered a Bosch one (more expensive but worth it), arrived yesterday and went on at tea-time today along with the new oil cap.

This time not only did the car start and idle - smoothly and on all 4 - but then I was able to do the entire rev range without missing a beat, then drove it round the block without issue, then took it for a run up the country roads to the castle and back.

Never felt an AUA pulling like that before beyond 3000rpm - it felt more like the take-off of a Tdi hitting the torque curve than the usually rather sedate acceleration of the AUA previously. Obviously a combination of the new injectors and a properly-working coil, but really very impressed. Going to fill up tomorrow and then see how the fuel-economy goes under normal use over the next few weeks.

As a final aside - the reason for buying the cheap coil late on the Saturday afternoon was that Amazon could get it to me on Sunday. I've had adequate experiences with cheap parts before (obviously lucky) and the main thing that it proved was even though the cylinder 1 output failed near-immediately, the rest of the unit was working so much better than the knackered OEM original at 17 years old that the engine was running better than it had done probably for years. Proof enough to warrant buying the Bosch given the improved running today.

 

[steve_c]

Never felt an AUA pulling like that before beyond 3000rpm - it felt more like the take-off of a Tdi hitting the torque curve than the usually rather sedate acceleration of the AUA previously. Obviously a combination of the new injectors and a properly-working coil, but really very impressed. Going to fill up tomorrow and then see how the fuel-economy goes under normal use over the next few weeks.

This definitely sounds like you've resolved the issues with your AUA and I'm really pleased for you. I'm expecting the fuel consumption to drop in tandem with the obvious increase in performance; hope you'll return and give us the latest figures in due course.

 

[Vorsprung durch Technik]

A great result Robin - pleased for you mate! Ive said similar in that a well maintained one is most definitely no slouch when pushing on. As with most things in life it really pays to go for Bosch or the original Audi part for reliability for that fit and forget peace of mind most of strive for.

 

[Edwrai]

A great result Robin - pleased for you mate! Ive said similar in that a well maintained one is most definitely no slouch when pushing on. As with most things in life it really pays to go for Bosch or the original Audi part for reliability for that fit and forget peace of mind most of strive for.

Depends on the part, for example Bosch spark plugs on the aua I heard weren’t recommended and NGK were the plugs that ran nicely


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[steve_c]

Depends on the part, for example Bosch spark plugs on the aua I heard weren’t recommended and NGK were the plugs that ran nicely

I went the other way and switched from NGK to Bosch Super 4 plugs. Very happy with the result.

 

[Edwrai]

I went the other way and switched from NGK to Bosch Super 4 plugs. Very happy with the result.

Interesting I know the lupo boys have had very bad experiences with the Bosch plugs on the AVY I believe the oem part is NGK


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[Robin_Cox]

Interesting I know the lupo boys have had very bad experiences with the Bosch plugs on the AVY I believe the oem part is NGK

7zap suggests NGK and an alternate Beru plug for the AUA originally so that correlates with the above. Mind you, like @steve_c I also fitted Bosch Super 4s when I replaced the leads (also now Bosch) last year and they were miles better than the really mucky unmatched non-originals that I found in there at the time.

In combination with the new bits they seem to be working nicely but I don't have a good scientific control to say that NGKs wouldn't be better in a properly-working engine : coming from such a poor starting point anything is better than it was right now.

 

[Edwrai]

Is the spark gap 1mm like it is for the avy? I would have thought so as they are very similar but they do have a different oil requirement.

Anyway the lupo gti forum has these issues with the Bosch plugs

“There seems to be a common thing with people changing plugs and using Bosch, followed by a misfire and having to change the HT leads due to the top of the spark having a different shape and bending the HT lead out of shape causing a bad connection.

Although I wouldn't say this happens to everyone and Bosch for some people work perfectly. Whether its to do with the age of the HT leads and how longs its been since they've been removed could be another reason for it, and be nothing to do with the spark”

Big can of worms of peoples opinions. At the end of the day, if they work for you, use 'em


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[Robin_Cox]

Driven to town twice and back and will be doing another run later (kids birthday party dropoff and pickup runs) - so 33 miles since I filled up this morning so far. I zeroed the trip computer which had settled on a DIS average of 34.5mpg in the 4 tank-fulls since Tom put the DIS in (fuelly suggests 34.0) doing normal duties. At the moment DIS suggests an indicated 47mpg average with a projected range of 350 miles (never done better than 230 in summertime previously). Will be interesting to see if this level of improvement carries on for the rest of the tank.

 

[enrih]

What is your idle rev counter?
Just cleaned MAP sensor, but check engine light still comes on with no fault codes visible on my VCDS- Lite.
Thinking of going the route of throttle body and EGR.
Same problems with fuel economy..??

 

[Robin_Cox]

When fully warmed up the car is idling around 700rpm or something like that, well under 1000. Distinct contrast to the Tdis that idle just under 1000.

 

[i love a2]

Hi I have a bby and aua both are good but the aua is the better car I think please update posts nice to here more on the petrol model s

 

[Robin_Cox]

If there are no obvious errors, I would strongly recommend having a look at the coil (ie, take it off and look at it from all sides) for the simple reason that unless it is very bad indeed it can contribute to a lot of problems without causing an overt error that will appear on VCDS. Also, have a look at the misfire count logs in VCDS - the car can be misfiring gently without an error coming up. With my car it was a bit uneven to begin with (non-existent maintenance record despite annual MOT passes suggesting a dodgy garage, rough idle, twitchy throttle response, rough spot around 1700rpm etc.), and openly reported problems with TB adaptation and EGR failure, so as explained upthread, I replaced both, followed by all 4 plugs and leads because it was clear the TB was full of crap, the plugs were dirty and the leads didn't look good either. We fixed all of those problems but from experience driving it there were still intermittent problems with bad running, even with the above done.

Advice from here suggested looking at the injectors (at 184000 miles the originals were unlikely to be good and proved to be filthy once taken off) - so I got a decent second-hand set here and had them refurbished / checked out by injectortune. Put those on - and it was then that the coil pack finally showed its problems by arcing through the casing to the engine block so the penny finally dropped and I tried a new replacement. In taking off the old one it became clear it had cracks all over the casing (hidden when installed) that result in weak sparks. Running on 3 cylinders (coil cylinder 1 output failed almost immediately on the new coil) the car was smoother than ever before with no misfire counts, so I bought a Bosch coil and this once fitted was an absolute revelation. Also fitted a new oil filler cap on top of the engine block as there was a burnt seepage mark around it, and the seal was very compressed - anecdotally these cause minor air admission problems. Now it's running like a sewing machine and the fuel economy apparently is ~10-13mpg better average.

 

[steve_c]

Now it's running like a sewing machine and the fuel economy apparently is ~10-13mpg better average.

If it feels right, it almost certainly is. I've followed this thread with interest, having an AUA A2 myself. As useful as I find VCDS (which is very useful indeed) it can't always be relied on to correctly pinpoint the problem area. As you may remember, I had endless fault codes, and occasional engine cut outs all of which resolved when I fitted a new exhaust - which was never flagged up with VCDS.

I'm keeping all your other issues stored up, and will stock up on the appropriate parts, so that I don't get caught out when I hit problems in the future; thanks once again for sharing this singularly helpful information.

I see that you had a new exhaust fitted. Did you replace the entire exhaust, or just the bit that was the MoT issue?

 

[Robin_Cox]

>thanks once again for sharing this singularly helpful information...

Not at all, it's been a huge learning curve for me as well - and I've learnt so much from questions I've asked here that if any of my experiences assist anyone else in the same position then I'm happy to share and discuss. I'm nowhere near as capable as the folk who have engine cranes and have replaced suspension components etc, but there is a distinct satisfaction in being able to take the bolt-on parts above the engine off and put them back together again and see a tangible improvement in the running of the car.

Sadly I didn't choose the exhaust - although it looked no worse than any of my other ones (both Tdis) at a cursory glance underneath, years of salted Scottish roads and neglect mean that the silencer had disintegrated inside, and then when they had it up on the ramp it became obvious that it was basically rust held together with silver paint and possibly melted on duct tape more or less from the silencer to just underneath the manifold. The cat was also knackered from probably years of running rich and lack of maintenance (weirdly the car had passed several years of MOTs maintained and MOTd by the same place with not even an advisory yet 6 months after the previous MOT I needed to completely replace all the suspension and brakes and all the bits I've mentioned above after years of neglect, suggesting they were more than slightly dodgy!). In the time available all my garage could get was what Dingbro could supply which is a rather generic no-name mild steel job - if I had had both time and money last year it would have been great to get something like the Infinity exhaust that has been mentioned elsewhere. This one still sounds rather grunty even though it is starting and running much better - it sounds better from inside the car than outside. So I believe that it is a cat back system (with a new cat).

My next mission is to try to reduce the significant amounts of oil entering the top of the throttle body, which suggests that the oil-air separator is hugely compromised. There are two possible ones for the AUA - early (square), and late (round).
Parts 19 or 19A

cylinder block with pistons; oil sump Audi A2 (A2) 2003 year Audi EUROPA 103005

cylinder block with pistons<br/>oil sump Audi A2 (A2) 2003 year Audi EUROPA 103005 spare parts

audi.7zap.com

My car's build number is bang on the changeover around Easter 2002 - technically from the VIN number it was built 175 cars after the switch, but the pipe that joins up to by the throttle body I thought was limited to the square one so it's a bit of a mystery. Not had a chance to put the car on axle stands to check around the back of the engine which is which a pain as I'm on holiday this week (half term). My other half so enjoyed having "her" car back yesterday that she's taken it to work today so no chance. Interestingly even she noticed that it is much faster than before. Besides which - it is raining, so I wouldn't have been on my back on the driveway either.

 

[steve_c]

In the time available all my garage could get was what Dingbro could supply which is a rather generic no-name mild steel job - if I had had both time and money last year it would have been great to get something like the Infinity exhaust that has been mentioned elsewhere. This one still sounds rather grunty even though it is starting and running much better - it sounds better from inside the car than outside. So I believe that it is a cat back system (with a new cat).

Robin, just pleased to hear that you replaced the whole system, even if it was through necessity. One of my bugbears is car owners who underestimate the importance of a clean exhaust set-up to performance and efficiency, let alone reducing the wear and tear on the engine. Nothing whatever wrong with a cheap and cheerful system beyond the fact that obviously it won't last for ever.

 

[Robin_Cox]

It's not so much that I voluntarily replaced the whole system rather than I have a garage who are engineers rather than check-list/bare minimum merchants. I trust them when it comes to stuff that they buy in when needed having cleared it with me, and they trust me when I supply piles of parts to be fitted on my hobby cars as part of a refurb (this trust has developed over a while - they don't do it for everyone). Every car I have has failed something on the MOT at one time or another - but when they've shown me it it is always genuine, not BS, and I would prefer it that way round to be honest.

 

[steve_c]

Another month on, wondering how your wife's A2 is progressing - particularly how the fuel stats are shaping up.

 

[Robin_Cox]

Hi Steve, the simple answer is that 'it depends who is driving' ; the first full tank ended up only being 34.8mpg (fuelly) which doesn't sound like much better. However, I only had it for a few days at the start of the tank when there was a DIS-indicated average fuel use in the mid to high 40s and predicted range in the 300s. Then two things happened - the average temperature here dropped several degrees, and I wasn't driving it. We ended up still going further on a 34L tank than has previously been seen (240-odd miles instead of 220), but the average indicated by DIS was back to mid 30s corresponding to the refill mileage. For what it's worth, my car (remapped 1.4 tdi) which is now being borrowed has gone from high 50s indicated commuting to low 40s on colour DIS since last weekend, so that suggests the fuel use goes with the driver. I was a passenger in my car the other night and it can be safely said that she enjoys the performance (more than I did)!

The 1.4i car is in for MOT since Monday - driveshaft seal on gearbox dribbling oil that has needed to be fixed - so I will have it back today or tomorrow, hopefully now also with a new oil separator and fitted oem undertray for the first time in our ownership.

 

[Robin_Cox]

And .. the (a) gremlin is back.

Second time in 5 days the same sequence of events : warmup starts normally (running engine to thaw out tailgate and prewarm the coolant for my other half to go essential shopping (!) .. but once it has been running for a couple of minutes on idle (while I was scraping windows), abruptly a couple of near-stall stutters followed by EPC / engine / ABS lights coming on (I suspect the latter is voltage related?), followed by the revs surging continuously from ~600-ish to around 1200ish and back down again.. This all with the engine idling, coolant temperature around 40 degrees or so. Error messages - from the ABS controller said 'Engine ECU' (and it cleared straight away using the reader when holding idle steady) ; engine ECU itself has two error counts - I think one was MAF sporadic implausible signal - ***, the other was sporadic air leak in manifold or similar (I know it was something to do with air but my memory is clearly flawed!!) . Clear these, they come back. EPC stays on but then goes away if you stop and restart car until the surging starts again. If you hold the car at 1200rpm on the throttle, it is as smooth as anything, no fluctuations or trembliness I was getting last year when there were sporadic midfires, and the misfire count isn't doing anything (all four cylinders on 0 counts).

So something seems to clearly be up with the mixture - I'm hoping to find something obvious like a pipe that is undone, but suspect it may be more insidious than that.

I've read suggestions of unplugging things stepwise (ie EGR) to see if there is a net improvement to eliminate possibilities, but any other suggestions appreciated. I'm not overly happy about the idea of spraying fuel around to find a leak, so anything less potentially pyrotechnic would be preferred!!

Back to the driveway - I've thawed out enough to have another look.

*** just looked it up again on the car : complete rubbish. The primary Engine ECU Error is 17961, Barometric / Manifold Pressure Signals, Implausible correlation.

Car just sat for 5 minutes on the idle as smooth as anything, up to 70-odd degrees coolant temperature without missing a beat, lambda is varying gently from -1% to +2%. So whatever the issue is, it is sporadic and possibly related to warming up / the automatic choke being on.

(45 minutes of websearching and another trip outside later)
One other thing I noticed - I had the oil cap on top of the engine off the other week when I took the plugs out. There was a bit of oily residue around it at the time (I've just re-read a thread from last year where I replaced this), but there appeared to be more today, so I've given the area a good clean and have re-seated the lid as tightly as I could - thinking based on some comments from (I think) @audifan in one of the threads that crankcase air leaks can be caused by the oil lid seals not sealing properly.

Engine again has just idled for 10 minutes without any issue at all, but I'm wondering if the filler lid was playing a part because it didn't feel very tight.

I'm going to have a look at the MAP sensor if it is warm enough tomorrow just in case giving that a clean helps - in fact, going back through my Ebay purchase record, I actually bought a new one of these last summer so if I can find how to access it and swap it over may well give that a go.