Refurbishing an AUA

R

Robin_Cox

Member
My other half's AUA is venturing into the 180,000s after many years of neglect. I redid the suspension and brakes & belts last summer, exhaust & cat was replaced at MOT. Various bits of internal trim being hard-touched or tidied up with tactical purchases sourced here from many of you. On the whole it's actually not a bad wee car at all.

However, although I replaced the throttle body & EGR, air filter, plugs & ignition cables last autumn, it is still pretty heavy on fuel - compared to some peoples' quoted economy. If I can save up the pennies this year, are there any suggestions on somewhere I could take the car to to get the AUA running really sweetly and somewhere close to its proper economy again (I'm assuming this would involve a strip-down and tidy up of the engine & fuelling / breathing parts) - or any other suggestions and thoughts if there was scope for a simple build? The lambda was replaced for the MOT as well, but the new one had to be fitted by cutting away the original connector suggesting it wasn't a like-for-like replacement, so I wonder if the mixture is still an issue (and if anyone has any lambda measurement figures I'd be able to compare with an ODBII reading to see if this is still awry I would be grateful).

Thanks for any ideas.
 
32-33mpg, mostly commuting around 6 miles each way or around town. 34 litre tank goes around 210 miles with my other half driving - I might be able to stretch a bit more distance out with light feet. To my mind it seems to be running rich, rather as if the choke is on permanently (when idling just after starting one can smell the petrol in the exhaust).
 
I get at least 40 mpg out of my AUA A2 for the same sort of driving. I have VCDS; let me know exactly what measurement you need and I'll do my best to help.
 
Hi,

if the mixture is out or the lambda isn't working correctly then you will have a stored fault code and probably the engine warning light on the dash. If you see that then you will not get the optimum economy.

Has the compression been tested? Is it OK?

Does the engine get to temperature? If the thermostat has never been replaced, its probably not working properly now and preventing it reaching the operating temperature. When the engine is cool it runs a richer mixture and uses more fuel.

Also, is the ECU seeing the correct engine temperature? The sensor has two parts and the ECU uses a different reading to the dial. If this isn't working and is telling the ECU that the engine is cold when it isn't, again you will use more fuel. You need to use VCDS to check this reading.

regards

Andrew
 
Hello,

thank you all. To answer the last questions first, as I'd had issues with stat / sensor in my 1.4tdi, looking at the temp measurements in the 1.4i was one of the first things I did. It's like chalk and cheese - even on a cold day (-5 here), starting at the house, it's at 90 degrees dashboard indication by the time I get to the village 2 miles up the road, so I think the thermostat is o.k ; in the Tdi it might get towards 80 as I get to work after 15 minutes (and the stat and sensor are both good now), but warms up fully on the dual carriageway.

Also, is the ECU seeing the correct engine temperature? ...

That's an excellent point actually - I've not tracked the ECU reading in the 1.4i for coolant temperature when driving, so of course even if the dashboard is reading correctly, if the ECU side has dropped out, that would make it run rich. Will do that when I next get a chance, although my cheap VCDS laptop connector won't speak to the Magnetti Marelli ECU (but my ODBII reader will).

Compression hasn't been tested - there were bigger issues to resolve last summer - what effect would this have & symptoms to look out for? Engine light not on recently but when it did it was throttle body (utterly filthy, put a clean one on) / EGR (also filthy and not working ; new EGR got rid of all of those codes, and cleaning, replacing and adapting the TB has eliminated the light although there are still sporadic "tb not completing adaptation properly" codes once in a while. Daft question - obviously, the TB needed to be cleaned, and the EGR needed to be replaced- should one do anything with the S-shaped metal tube that joins the two, and other pipes joined to the TB?

I don't know how much of the economy issues are the car, and how much is the normal driver, mind you - she has very heavy feet (on our Citigo, measured reliably over 3 years approximately 15mpg heavier than me at 45mpg compared to considerably >60 for similar journeys).

@Olerype
"Get close to 60mpg with the AUA. That is exactly the same as the TDI90. Quite amazing."

Can we swap ? (either car or my partner - I'm not bothered as long as it sorts out the fuel expenditure.....) :)
 
Robin_Cox said:
Hello,

thank you all. To answer the last questions first, as I'd had issues with stat / sensor in my 1.4tdi, looking at the temp measurements in the 1.4i was one of the first things I did. It's like chalk and cheese - even on a cold day (-5 here), starting at the house, it's at 90 degrees dashboard indication by the time I get to the village 2 miles up the road, so I think the thermostat is o.k ; in the Tdi it might get towards 80 as I get to work after 15 minutes (and the stat and sensor are both good now), but warms up fully on the dual carriageway.

Also, is the ECU seeing the correct engine temperature? ...

That's an excellent point actually - I've not tracked the ECU reading in the 1.4i for coolant temperature when driving, so of course even if the dashboard is reading correctly, if the ECU side has dropped out, that would make it run rich. Will do that when I next get a chance, although my cheap VCDS laptop connector won't speak to the Magnetti Marelli ECU (but my ODBII reader will).
Click to expand...

Hi, Sounds like the thermostat is OK, worth checking the ECU temperature though.

Robin_Cox said:
Compression hasn't been tested - there were bigger issues to resolve last summer - what effect would this have & symptoms to look out for? Engine light not on recently but when it did it was throttle body (utterly filthy, put a clean one on) / EGR (also filthy and not working ; new EGR got rid of all of those codes, and cleaning, replacing and adapting the TB has eliminated the light although there are still sporadic "tb not completing adaptation properly" codes once in a while. Daft question - obviously, the TB needed to be cleaned, and the EGR needed to be replaced- should one do anything with the S-shaped metal tube that joins the two, and other pipes joined to the TB?
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Lack of compression: uneven running/idle, lack of power and torque. Poor running = bad MPG.

I would not have though the metal tube would get blocked as the bore is relatively large and its very robust so it should not leak. The one time use crush gaskets should be renewed when refitting/replacing the EGR and if its new or cleaned then the EGR adaption should be run. Failure to run the EGR adaption can damage the valve and/or cause mixture problems and poor running of the engine (and high fuel consumption as a result). If the pipe is blocked then you will get an EGR insufficient flow error.
Mixture problems will be logged as a fault though in the ECU, for what ever cause. Most likely "Long Term Fuel Trim Additive Air System too Lean". If you see that then your MPG will be bad.

Robin_Cox said:
I don't know how much of the economy issues are the car, and how much is the normal driver, mind you - she has very heavy feet (on our Citigo, measured reliably over 3 years approximately 15mpg heavier than me at 45mpg compared to considerably >60 for similar journeys).

@Olerype
"Get close to 60mpg with the AUA. That is exactly the same as the TDI90. Quite amazing."

Can we swap ? (either car or my partner - I'm not bothered as long as it sorts out the fuel expenditure.....) :)
Click to expand...

If you don't have any mixture trim faults logged and compression is good then the injector spray might be sub standard. I can't imagine they are still good after 180K miles. You can send them off the ultrasonic cleaning or get a brand new set of OEM injectors from eBay for ~£100.

regards

Andrew
 
Again, thank you - that's definitely worth a go this spring (injectors) ; but first up I'll have a crack at the ECU temp sensor measurement when I next have access to the car. The EGR was adapted when it was replaced (with new washers all round on both this and the TB) and that eliminated all of the EGR fault codes that have never returned, unlike the sporadic TB adaptation message. Idle is intermittently uneven, but I assumed that was the throttle body. One symptom of this is that the car doesn't like running on a part throttle at ~1600-1700rpm (ie, 25-30mph in town) whereas if you floor it it runs fine and spins cleanly up to the redline.
 
For the sake of some petrol and £5 for some injector cleaner - is it worth adding some to a tank full and taking it on a decent run?

Only had my AUA a short time but have done a couple of long runs and consistently got 46 mpg which I thought was reasonably good given that the engine is 'old technology'. Have not checked but I am guessing that will drop to high thirties round town. Don't think I'd expect any more.
 
More feedback on my AUA project - which came to a head in the last few days with a chronic and undriveable misfire (cyl 2 and sometimes 4) which rather encouraged me to get to work on the next steps as my other half has now commandeered my remapped colour-DIS BHC for commuting.

Just to recap - last year on the AUA I replaced throttle body & EGR, new Bosch plugs and cables ; catalyst and exhaust were done for the MOT. This helped but there have still been intermittent bouts of rough running and poor fuel economy since that started going downhill recently.

@audifan and @ajsellors suggested changing the injectors last year, I sent @Fallan's AUA injectors away to injectortune for an ultrasonic clean and refurb (o-rings and filter buckets). They came back shiny with a clean bill of health, so I built them up with the rail, then stripped the pipework above the engine down yesterday to uncover the injector rail. Noted a certain amount of oil above the the throttle body that may be coming back from the oil separator rubber pipe (suspect the separator probably has never been changed).. another job for another day.

After a bit of a fiddle getting the push rivets holding the injector loom onto the rail undone (invert the unbolted rail and use a small screwdriver to push the central bit out) , I managed to remove the existing rail - which was pretty filthy with all four injectors looking burnt in the centre by the wee injector holes and grease / grime all over the outside ; then put in the new rail and put everything back together again. I had to remove ignition lead 4 from the coil to get the big plastic box above the throttle body back into the space again, put all the pipework back together and ready for a test, bonnet off.

Plugged in the ODB reader, and started up. It seemed smoother than before generally, but after a few seconds it was obviously running on 3. #4 (but no others) was ticking up the misfire count, so I cleared it, and it happened again. Then I noticed the narrow but intense plume of smoke coming out of the engine area.. so switched off. The smoke was coming from the coil pack- whereupon I noted that the lead for #4 was still lying unplugged. It stopped smoking after a few seconds, so I plugged in the lead.

The car then restarted - and ran on all 4 fine for a couple of minutes - until the misfiring started. Cylinder 4 only to begin with, but eventually an occasional contribution from 2 and 1 at one point.

I then realised that the coil pack was probably shafted, and sure enough, the wall of the socket for cylinder 4 had arced all the way through and was presumably earthing across to the metal.

Got a cheap coil pack yesterday - fitted it today - in doing so taking off the original coil. Not only was the cylinder 4 socket burnt through (probably my effort!), but I then realised that the entire casing was cracked in several places adjacent to the bolt holes and the potting compound on the back was also coming away from the casing - so probably the coil pack has been electrically compromised for some time since before we had it - I understand now from a bit of reading that this happens because of heat and vibration etc. So - if you've got AUA misfires - apart from all of the other possibilities raised by @depronman & @Vorsprung durch Technik among many others - have a look at the coil pack's structural integrity (it needs to be taken off to look behind it and turn it around).

The new coil started instantly on all 4, smooth as anything, no misfires in 10 minutes of idling on any cylinder and smooth through the rev range. In combination with the new injectors, this is the biggest step forward since replacing the throttle body & fixing the EGR last year. Fingers crossed.
 
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Robin_Cox said:
The new coil started instantly on all 4, smooth as anything, no misfires in 10 minutes of idling on any cylinder and smooth through the rev range. In combination with the new injectors, this is the biggest step forward since replacing the throttle body & fixing the EGR last year. Fingers crossed.
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Robin, I'll be very interested to hear your mpg figures after this once you've had an opportunity to do some decent mileage.
 
steve_c said:
Robin, I'll be very interested to hear your mpg figures after this once you've had an opportunity to do some decent mileage.
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So will I .. you've got to bear in mind the weight of my other half's feet as she's looking forward to getting it back once I sign off on the job so it will probably be only a run to the fuel station and back that I get, but even taking this into account an improvement will be an improvement.

I paste the last 12 months' fuelly record. Bear in mind that this has been with a car with suspect maintenance record, used almost exclusively on 6 mile commutes and otherwise in town by someone with a healthy disregard for climate change - but comments from other AUA owners averaging high 40s, into the 50s etc mpg - would suggest that improving the way the engine is working could have some impact. We'll see.

Any thoughts on the apparent oil separator saturation and effect that this could have on the way the car is running (oily TB) would be appreciated. The build number compared with 7zap's quoted changeover point suggests that it needs the later design of round oil separator, but I thought that these didn't have the rubber pipe connecting with the air box above the throttle body.
 

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Robin_Cox said:
So will I .. you've got to bear in mind the weight of my other half's feet
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I suspect that it's less the weight of her feet, more the inappropriate selection of gear. Driving in too high a gear is the most reliable way of burning through unnecessary petrol.
 
I've been a passenger in the car a few times to my eternal regret (given that I pay the fuel bills). Trust me when it comes to her feet - there are black holes that are markedly less dense... - I used to average around 20% better fuel economy driving the Citigo on the same routes so I have a pretty good idea of the differences in style.
 
Hi Robin
Just saw your last few posts.
I had the same kind of troubles with my 1.4 AUA. It was indeed the coil pack and also one of the spark plug cable. I believe I posted a picture at the time. The connector was broken in the rubber that connects to the spark plug.
I also have a heavy right foot and still average 44mpg, calculated with the receipts and the mileage.

Long live your A2
 
Oil filler cap on the engine cover also has a bit of seepage (long term / dried on) possibly suggesting it has a slight leak - although I can find lots of caps that seem to be for Tdi engines I am having issues finding one that would be suitable for an AUA (or else I'm over-thinking it and they're all o.k?). Any recommendation of a part?
 
Robin_Cox said:
Oil filler cap on the engine cover also has a bit of seepage (long term / dried on) possibly suggesting it has a slight leak - although I can find lots of caps that seem to be for Tdi engines I am having issues finding one that would be suitable for an AUA (or else I'm over-thinking it and they're all o.k?). Any recommendation of a part?
Click to expand...
Not a recommendation as such, but eBay is telling me that this is the correct item for the AUA A2:
www.ebay.co.uk

Audi A1 A3 8P A4 B6 B7 Oil Filler Cap Lid New Genuine 06B103485C | eBay

Find many great new & used options and get the best deals for Audi A1 A3 8P A4 B6 B7 Oil Filler Cap Lid New Genuine 06B103485C at the best online prices at eBay! Free delivery for many products.
www.ebay.co.uk

That part number is easily available cheaper of course.
 
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Thank you! I'm normally pretty good at sourcing the part number from 7zap but I was having a nightmare with that one. Went for the Febi version in the end to keep on top of the pennies but the link was much appreciated.
 
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