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www.audifans.net :: View topic - 00537 - lambda 02 sensor regulation - code. ACE 16v
 
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EightyWay
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PostPosted: Sun Apr 26, 2015 8:04 pm Reply with quote Back to top

Thanks Hoolio, I might just take you up on that. I include a few more pics to confirm it's the right one. 4 bolt connecting to the CAT. If so we'll PM. Do the mating surfaces need sealant as well as a new gasket? Does the ring seal at the other end need sealant/gum?



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4 bolt flange
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Mounting bracket
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Exhaust manifold to downpipe
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hoolio
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PostPosted: Mon Apr 27, 2015 10:51 am Reply with quote Back to top

Ahh sounds like they're different as they have 4 bolts to manifold and only 3 to the cat although 1 of them hasn't got the connecting collar to cat on it as it was wafer thin the part number being 893 253 101 B if I recall,as it was a few years ago and I'm getting on a bit,my cat had 3 bolts to the downpipe and 4 to the exhaust.

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EightyWay
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Joined: Jul 17, 2014
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PostPosted: Mon Apr 27, 2015 12:03 pm Reply with quote Back to top

A mate of mine has that version too including the CAT (from a 1.6) so I was thinking of swapping the whole unit or order a new downpipe online. They're pretty cheap considering. I may start the job and decide on the fly which route I take.
 
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EightyWay
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PostPosted: Mon May 11, 2015 7:57 am Reply with quote Back to top

I have a new downpipe from BM Catalysts, just waiting for a gasket now. I did a temp fix to the leak.

On inspection of my spark plug leads I notice 3/5 were damaged.
Lead 1 is split boot
Lead 2 has light abrasion
Lead three has deep abrasion
Lead 4 seems fine - Knock sensor has no visual damage.
Coil to dizzy seems fine

I bought a complete set (NGK) - Does anyone know how to put the knock sensor on a new lead?
 
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Mikes2
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PostPosted: Wed May 13, 2015 3:09 pm Reply with quote Back to top

Don't think it's a knock sensor. - They're on the block

You would need remove the end from the lead to swap it over or re-use the original

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EightyWay
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PostPosted: Sun May 17, 2015 8:13 pm Reply with quote Back to top

Ok, replaced the downpipe. The old one wasn't too bad, just an ugly bit of welding I'll refurb it and keep it as a spare. I think there was a leak as the car seems quieter on the motorway, and a buzzing that came at 130kph has gone. Nice, but the lambda code is back!

I swapped out my isv with a coupe with the same engine - it did seem that my isv seemed to make his car run more poorly and mine a little better. I was comparing the engine load increment from the diagnostic scanner.

I'll wait until I have done the ht leads but it looks like the isv is next....although I may recheck the pickup and return tubes in of the fuel pump in the tank. Injectors may need to be looked at again - or possibly the differential fuel pressure regulator...
 
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EightyWay
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PostPosted: Tue May 19, 2015 4:29 pm Reply with quote Back to top

I think I will revisit the injectors at this stage. I did clean them and check the spray. The injectors did deliver exactly the same volume, but not quite a conical fine mist. Step 1. leave them in a jar overnight to check for leaking. Then, I plan to do a "hat off" clean (i'll buy some spares just in case I mangle something). Maybe hit it with some ultrasonics. I will include the cold start injector in this process. I need to rule out the possible fuelling issues causing the Lambda code. This code is relentless!
 
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jamiecoysh
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PostPosted: Fri May 22, 2015 9:19 pm Reply with quote Back to top

fixed mine turned out to be incorrect mixture setting, was running too rich
 
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EightyWay
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PostPosted: Mon May 25, 2015 4:21 pm Reply with quote Back to top

Nice one! AFAIK all the mixture settings on my one (16v ACE) are controlled by the ECU. Are you talking about the secret screw near the metering head? Cheers
 
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jamiecoysh
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PostPosted: Tue May 26, 2015 8:02 pm Reply with quote Back to top

theres a tiny adjustment screw on the metering head itself, people will tell you not to play with it but all these cars are so old now that sometimes manual adjustment is necessary. the garage turned it a small amount and it worked and was perfect. The ECU controls the mixture on the 3A engine too so I don't think you have too much to loose by trying it
 
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EightyWay
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PostPosted: Tue May 26, 2015 9:11 pm Reply with quote Back to top

Thanks, I am at the stage that I have replaced everything that was potentially damaged and about to do more speculative replacements like new injectors and isv etc. It was going to get pricey - with no guarantee of success.

Do you adjust the screw whilst the car is running? If so, I could the scan data to observe fluctuations and dial it in. I have data from a smooth idling coupe to compare with. Who knows the screw might have been tampered with already!
 
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EightyWay
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PostPosted: Wed May 27, 2015 11:42 am Reply with quote Back to top

Is this what we are talking about?



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Not sure what the left picture is of!
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Mikes2
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PostPosted: Wed May 27, 2015 12:31 pm Reply with quote Back to top

that left image is the head bolt sequence.

you adjust it while running but DO NOT rev the engine with the tool in place.

You must remove the tool to rev the engine after each adjustment. No more than 1/4 turn at a time.

I'm not convinced this will cure a lambda probe code
 
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EightyWay
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PostPosted: Sat Jul 25, 2015 8:24 pm Reply with quote Back to top

I didn't end up fiddling with the fuel mixture.

The cat let go this week - rattling, so I'll fix that first. Also, I have a replacement ISV on the way too but I think that's got lost in transit. Anyway, the lambda code saga continues...
 
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EightyWay
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PostPosted: Tue Aug 04, 2015 10:05 pm Reply with quote Back to top

The CAT monolith was separated from the casing causing the rattle. Apart from that the CAT was intact. Lambda code remains - at least it's consistent!

I think I will go back to fuelling - I believe I have leaky injectors so i'll start testing there.
 
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EightyWay
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PostPosted: Wed Aug 26, 2015 7:59 am Reply with quote Back to top

Ok, three out of the four injectors were leaking. There wasn't much fuel in the jars after being left overnight, but still. I got a deal on a new injector replaced it with a leaky one - already it feels smoother and because there was no fuel in the bores it started easier. Hot start was always good but an overnight/next day cold start meant I had to crank twice.

I will try and clean the injectors one by one using the disassembly method. I now can also compare the spray to the new one. The spray did look good when I tested them last but I didn't really know what I was looking for.

My question is, are injector leaks impossible to stop after they start? Or, am I wasting my time trying to clean the leaky ones?
 
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Mikes2
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PostPosted: Wed Aug 26, 2015 8:54 am Reply with quote Back to top

not sure if they can be rebuilt. New injectors are typically ~£40 a time so it may not be cost effective.

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EightyWay
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PostPosted: Thu Aug 27, 2015 9:08 am Reply with quote Back to top

I removed the hat and sprayed carb cleaner through one last night. Worked better than expected. The spray pattern became evident I will have a few tries at cleaning before I get some new ones. Just curious I guess. I can new ones at €45 each from Germany if it doesn't work out. Cheers
 
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EightyWay
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PostPosted: Thu Oct 01, 2015 12:28 pm Reply with quote Back to top

Update: The injectors are still leaking but only on certain cylinders which made me think that only some were leaky. So they will be swapped out with new ones as we discussed. That's fine, but I don't believe these affect my rough idle/lambda issue.

My current hypothesis is that there is wear in the Mass Airflow Potentiometer at the idle range. This corresponds with the scope data which I posted initially (bright green line - engine load). I will test the potentiometer (BOSCH F026T03024 - I believe) to check if the values are within spec and if there are rough readings around the idle position. If necessary, replace.

I saw this was common with NG engines, so any insights would be welcome.
 
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EightyWay
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PostPosted: Mon Oct 05, 2015 8:21 am Reply with quote Back to top

After some resistance testing there is a significant jump in the readings given by the potentiometer, an indication that it has gone bad. I did a second test taking the voltage from pins 1 and 2 (4.83 volts) and the resistance from 2 and 3 (0.9v) - idle for 2 mins. This puts the potentiometer slightly above specification I will adjust the potentiometer adjustment (different to the one earlier in this post) screw slightly to bring it back into spec.

With the jump in readings on the first test I expect to buy a potentiometer but it's worth a try before I shell out €180.

I also tweaked the throttle body stop screw. Strangely the Lambda code didn't pop-up this weekend. We'll see if that lasts!
 
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EightyWay
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PostPosted: Thu Oct 15, 2015 7:02 pm Reply with quote Back to top

Ok, my target was to get the voltage reading below 0.8 volts whilst back probing pins 2 and 3 of the idle mixture potentiometer. In theory I succeeded but the values fluctuated greatly and there were only moments where the readings would stay below 0.8v. Rough idle remains.

The next step in my diagnosis was to remove the potentiometer connector (at idle) whilst the car was hooked up to the live data feed. The idle increased (like unplugging IAC) and all other readings levelled out (timing, rpm etc). It confirmed the bright green line refers to the "work load" parameter.

The original part is: 3437224037
It has been superseded by parts: 3 437 010 061 (€90) and BOSCH F026T03024 (€180). I will go for the cheaper one (both are Bosch). I have heard of Chinese carbon tracks but I haven’t been able to source them.
 
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EightyWay
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PostPosted: Tue Dec 08, 2015 9:46 am Reply with quote Back to top

Anyone know where to get these parts?
The original part is: 3437224037
It has been superseded by parts: 3 437 010 061 and BOSCH F026T03024

It seems that production has stopped - has anyone has success in finding one? I believe it is the same as the NG engine.
 
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Mikes2
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PostPosted: Wed Dec 09, 2015 4:28 pm Reply with quote Back to top

Looks like it was used on a lot of cars.

See Bosch Tradition

http://www.bosch-automotive-tradition.com/en/internet/automotive_tradition/parts/reproduction/motor/einstellpotentiometer/einstellpotentiometer___mit_teaser.html

Is there an Audi number on it at all ?

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EightyWay
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PostPosted: Tue May 31, 2016 5:32 pm Reply with quote Back to top

I ended up replacing the potentiometer with a new unit (which also included a new air flow meter). Even after all the fettling with the mixture settings there was still no change in the running of the ACE engine.

Recently I have experienced more surging (1200 rpm to 400 rpm) which often leads the engine to cut out. Swapping out the ISV made it worse (I think the old one is rusty and sticky which helped).

I have done what I should have done from the start - ordered an manometer to run fuel pressure tests. Which is where the original lambda code pointed to. My car happens to have 2 pressure regulators (one in the tank and one on the airflow meter) either of which could be acting up at idle. The only other part which may be acting up is the metering head (I have seen seal refurb kits for these). Hopefully a pressure test will indicate any problems there too.

I don't have a question at this moment in time. This is just an update, any comments are welcome though!
 
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