00537 - lambda 02 sensor regulation - code. ACE 16v

Posted: Mon Jan 12, 2015 10:30 pm

Hi, my car is running great but still suffers from the following symptoms:

1. Rough idle
2. Noisy fuel pump
3. Wont drink the last 10 litres of fuel
4. Recurring 00537 lambda code

00537 - lambda (oxygen sensor) regulation
08-10 - Control limit surpassed - Intermittent
Readiness: N/A

The Rosstech wiki states the following regarding the code:

Possible Symptoms
Lambda Control inactive
Engine running rough

Possible Causes
Wiring and/or Connector(s) from/to Lambda Sensor(s) faulty
Lambda Control/Sensor(s) faulty
Injector(s) faulty/blocked
Fuel Pressure Regulator faulty
Fuel Pump faulty
Fuel Tank empty
Vacuum/air leaks

Possible Solutions
Check Lambda Control/Sensors
Check/Repair Wiring and/or Connector(s) from/to Lambda Sensor(s)
Check/Replace/Clean Injector(s)
Check/Replace Fuel Pressure Regulator
Check/Replace Fuel Pump
Check Fuel Level
Vacuum/smoke test hoses/valves and replace leaking ones

The obvious starting point is to look for vac leaks, one year on I think I have "exhausted" that possibility (inspected most hoses extra clamps, new throttle body gasket, cleaned injectors, new injector seals etc, fuel lines cleaned). The car is now running much better, but just a bit shaky at idle and the noise of the fuel pump.

Next weekend I will be swapping out the Lambda sensor, gearbox mount (victim of the the rough idle) and testing the injectors.

I do, however, suspect something fuel supply related due to a noisy and hard working fuel pump. The former owner said he had to replace the fuel pump right before selling the car to me - so perhaps an underlying issue or he just replaced it with a cheap replacement (or incorrectly fitted).

A sticky fuel pressure regulator could be causing too much resistance (an ignorant guess) - I read somewhere that you could stick your tongue on it to test suction which sounds odd - is there a simple way to test one? I do have some scope data. The line(turquoise) is at idle and the wave form is revving it a bit. I will compare this with a mates ACE engine to see what his levels are.

For reference the green line is engine load data and at idle it fluctuates a lot which seems to correspond to the rough running. I hope that I can measure improvements in that area.

After all that I bet you it's just a vac leak somewhere!

Posted: Tue Jan 13, 2015 8:59 am

Is the idle rough all the time or only when the car is warm.

The lambda sensor doesn't get used straightaway - there's about 30-45 seconds of warm up before the ecu uses the signal.

When the pump got replaced, there should have been a new filter fitted at the same time. The pump also needs to be mounted correctly.

Posted: Tue Jan 13, 2015 6:35 pm

Yes, the idle is a little rough all the time no matter how warm/long the engine has been running. The right gearbox mount might be enough to rectify the shakiness. But that will still leave me with the lambda code and the noise.

Yes, the filter was not replaced together with the pump. At some stage the fuel filter had been replaced but it was clear that it was not new. The fuel filter has since been replaced (with no perceivable change as to how the car runs). In its history the car has been standing for a period of 5 years 2008-2013.

The jury is out on how well the pump is mounted - just need to have a look I guess. It is an avant and it is accessible through the boot I believe.

Thanks Mike

Posted: Tue Jan 13, 2015 10:33 pm

ill be keeping my eye on this as I have the same problem. Checked for vacume leaks etc and was thinking about changing the lambda but the garage said if its passed its mot then it must be working correctly.

Posted: Wed Jan 14, 2015 1:55 am

Yes, my one has just passed the Irish NCT, like MOT. If I recall it had a reading of 1.02 with a threshold of 1.03 based on their readings I will check up what those values mean.

Posted: Wed Jan 14, 2015 1:28 pm

is the pump in the tank on these ?

Posted: Wed Jan 14, 2015 8:23 pm

Yes, I was looking up part numbers yesterday and came up with a BOSCH 0580254040. I have seen discussions about the flow rates of the 040. I have a Mann WK 725/1 filter for it (but the last one is almost new so I'll hang on for a the new pump if it is required).

On another note, I just came back from some long distance driving in serious conditions. These cars are awesome when the weather gets bad!

Posted: Thu Jan 15, 2015 10:08 am

I suspect you may have the wrong pump or it's not been pushed down into the basket properly - that would be why you're not able to use all the fuel in the tank

Posted: Thu Jan 15, 2015 9:27 pm

Yes, that is starting to look like the case.

Posted: Sun Jan 18, 2015 11:25 pm

So I replaced the lambda and the gearbox mount yesterday anyway. Surprise, surprise, not much changed and the lambda 00537 code has returned.

I did a quick investigation of the fuel tank/pump. There appears to be quite some amount of tampering in that area (like hammering the basket loose with a screwdriver). In the photo there appears to be something yellow between the basket and the pump filter.

I think I'll make an inventory of exactly whats broke on my next inspection, it seems highly likely that some of the plastic clips have perished.

Posted: Mon Jan 19, 2015 1:39 am

you likely have a fuel pressure problem. If you fix that, you'll likely also sort the lambda probe code.

Not for the 16v but 0537 code could be

-Fuel tank empty at least 10 litres
-Fuel system pressure too low
-Failure of spark plugs, ignition coils
and ignition output stages
-Ingress of air to G70
-Leak in exhaust system up to catalyst
-Faulty lambda probe
-Fuel system pressure too high

things to check

-Fill up fuel tank
-Recify air leak
-Test lambda probe
-Test fuel system pressure
-Check hose connection intake manifold/
pressure regulator (fuel shut off
valve on overrun
-Check fuel return line of fouling, kinking
and damage

Posted: Tue Feb 24, 2015 11:05 pm

Ok, I took another look at this over the weekend. I checked for vac leaks with by spraying throttle body cleaner on the joins of the intake system. No leaks.

The fuel pump was next. When I removed the Pierburg long body pump I saw that 6 of the 9 mounting grommets were sitting in the bottom of the basket and a clip at the top was loose. So I set about removing the basket what a PITA! I ended up lengthening a oil filter remover and eventually it came free. Reassembled the basket, cleaned up the debris in the base of the basket and set about reassembling, still a PITA. I did run the pump briefly - it really is noisy.

So in this case the pump was indeed incorrectly assembled. The grommets could have restricted fuel flow and the pump could move about. I will report back on the codes and I will recheck the fitting of the pump. I am considering replacing the pump, but I fear they are all noisy. The car run the same as before.

Posted: Wed Feb 25, 2015 11:11 am

is this with all the carpets and trims back in ?

They're generally not too bad for noise if all the soundproofing is in place.

It's possible the pump has been damaged with the incorrect assembly. If you do replace it, replace the filter as well

Posted: Wed Feb 25, 2015 3:20 pm

Yes, all the trim and soundproofing is back in place. I have a new fuel filter ready to go although I replaced it not too long ago. The tank is clean.

I am going to check if the pump didn't shake itself free again, if not I'll change the pump. I couldn't find any part numbers on the pump (Pierburg type). Is this normal?

Posted: Wed Feb 25, 2015 5:04 pm

I'm guessing you have an 80 avant 16v here

Yours is #3 - 895 906 089 E

Do you have the pressure damper (#4). It's not clear from the pictures earlier

Posted: Wed Feb 25, 2015 8:14 pm

Wow, awesome Mike! I did take some pics during the reassembly. Here is the information I have:

Seal ring (not on diagram) 321 919 133
1. Pump 150mm long - Pierburg?

4. Pressure damper/accumulator
Bosch 0 438 170 052, Audi 447 133 441

There seem to be many different setups.

Posted: Thu Feb 26, 2015 8:33 am

7.21651.50.0 is the Pierburg part number.

Appears to be widely available if you put the number directly into your favourite search engine

Posted: Sat Feb 28, 2015 10:32 am

Thanks, I will report back when fitted.

Posted: Wed Mar 11, 2015 11:21 pm

Ok, fuel pump fitted. The new pump is much quieter. Possibly there were some kinks in the feed and return lines restricting flow. I did my best to ensure no blockages. The car runs similar to before - perhaps a little stronger. Idle still rough.

Overall I am happy with the new pump, but I did get the 00537 code again. I am a little concerned with the fluctuating engine load parameter values at idle. Does the TPS give the engine ECU data for the "engine load"?

Next steps check the injector spray with the new pump. Test the TPS. And check for exhaust leaks.

Posted: Sat Mar 14, 2015 1:12 pm

Has all the electrical wiring been checked as ok ?

you can use a Mityvac handpump for vacuum testing

Posted: Sat Mar 14, 2015 7:36 pm

Yes, the electrics are all back to normal. Everything working including Vagcom. Injector spray was good. Sprayed all intake joins and injectors with intake cleaner - still no change in engine tone. If there is a leak in the intake it'll be very small, so small that I doubt I'd see anything in a smoke test. For the smoke test I was think of cobbling together a charcoal in a jar with air blown through, but I am not so sure where to attach it to.

I'm going to take a look at the exhaust manifold first - removing the heat shield and have a look. There hasn't been any smoke in the engine bay which is why I have been ignoring an exhaust leak as a possibility until now. Another possibility is the join before the cat, I may get a new seal for that.

My multimeter is on the blink so no testing the TPS today - I've tried it before but never got anything meaningful out of it.

Posted: Sun Mar 15, 2015 7:56 pm

OK, I was wondering if there is supposed to be a sealing O-Ring between the downpipe and the CAT? I was thinking of this one: 893253137D

(6 months ago) I noticed that one bolt was not fastened between the cat and downpipe because the lambda was in the way (sheer laziness on the former fitters part) - I replaced the bolt. I am now assuming more corners were cut in that area. I am not sure which part was replaced at the time, I assume the CAT and Lambda.

Recently I removed this join to get access to the gearbox mount listed earlier in this thread. There was no ring there, it was just a 4 bolt flange on flange mating surface. Possibly a ring could have fitted between the two (creating a seal). There was no sealant, gum on the join.

My exhaust setup is original audi, Audi 80 avant 2.0 16v ACE engine. An air leak right before the lambda sensor can't be good right? Should my car have such a sealing ring? If so, would its omission be consistent with my Lambda 00537 code?

Posted: Sun Mar 15, 2015 10:34 pm

#27 = 8A0 253 137 A

Posted: Mon Mar 16, 2015 8:36 am

Thanks, they all see to have the O ring seal on them. I have ordered a ring and see if it fits. My 00537 code is classed as intermittent so I am not sure if this will make a difference but either way the exhaust needs to be sealed.
My one has a 4 bolt pattern and looks like this one:

Posted: Fri Mar 27, 2015 4:04 pm

Hi, I got a few more gaskets delivered - intake manifold, exhaust manifold & downpipe->cat sealer ring. I have been doing plenty of background research (ScannerDanner - engine diagnostics) and also comparing side by side diagnostics with another 16v. Whatever I do the vac leaks need to be retested, possibly whilst running live scope data which will help me identify rpm drops/gains.

I was planning to do this tomorrow, but a my heater matrix has started generating steam again so that will keep me busy this weekend...

Posted: Mon Apr 13, 2015 9:21 am

Update: I had a look at the seal ring and it was in place and seems to be correct. What I did notice was some welding and a small hole on the weld of the downpipe. I am not sure whether to:
1. Replace the downpipe
2. Plug the hole with Gum to see if the code stops
3. Weld the hole in the downpipe
4. Swap over to a 3 bolt cat - downpipe setup that a mate has lying around (from a 1.6)

When removing the downpipe from the 1.6 we sheared off two of the exhaust manifold to downpipe bolts. This has got me nervous about replacing the downpipe fearing I will do the same on my own working car. Any tips, or should I just plug the holes and see if it helps? Or is this job for the pros...

Anyway, here are some pics to illustrate the downpipe welding and leak(s)

Posted: Mon Apr 13, 2015 1:01 pm

That looks in a bit of a state.

I'm guessing you mean studs on the manifold to downpipe. Lots of release agent in advance - Plus Gas is what I prefer to use. If you break one, it's manifold off time usually although sometimes you can drill them out with it still in place. The other alternative is to use a dremel to cut the nuts off

Is yours a 2 port or 3 port ?

Posted: Mon Apr 13, 2015 1:05 pm

I have a small butane torch. I think it is up to the job. Mine is the two port version.

Posted: Mon Apr 13, 2015 1:09 pm

That's a pity. Got a 3 port downpipe sitting doing nothing

Posted: Fri Apr 17, 2015 4:15 pm

I have 2 of these currently being used as a squat for various critters if you need 1.