AUA 1.4 misfire cylinder 2 - trim readings

tuizner said:
hmm - same results on the "old" sensor -

so either
both are faulty
the wiring diagram is wrong
or I have used the wrong diagram but I think the AUA has the mm-mpi system?

Audi Workshop Service and Repair Manuals > A2 > Power unit | MM-MPI injection and ignition system (4-cylinder) | Mixture preparation system, electronic inj.,Gas | Checking components | Checking lambda probe heating for lambda probe before catalytic c

A2 > Audi Workshop Service and Repair Manuals > Power unit | MM-MPI injection and ignition system (4-cylinder) | Mixture preparation system, electronic inj.,Gas | Checking components | Checking lambda probe heating for lambda probe before catalytic converter
workshop-manuals.com
Click to expand...
The A2 wiring schematic I have, (downloaded from Audi Erwin), only shows the engine version with individual coil pack circuit.
Is the cyclinder 2 thing only on the single coil pack version of the 1.4? If so, that might be significant.
Mac.
 
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PlasticMac said:
The A2 wiring schematic I have, (downloaded from Audi Erwin), only shows the engine version with individual coil pack circuit.
Is the cyclinder 2 thing only on the single coil pack version of the 1.4? If so, that might be significant.
Mac.
Mac.
Click to expand...
yes single coil pack
 
interesting

Elsa looks to suggest there is no column 1 reading for my 2000MY AUA....

1690718661853.png
 
The ECU, for the twin spark engine must be quite different from the individual coil pack version. So, I'm guessing, the OBD diagnostics are different too, and the APE lable file that vcds uses for the AUA does not match it fully, hence errors.
We had a similar problem with the FSI, which is why a new, A2OC FSI, (BAD), file was recently created FOR it.
Maybe an AUA specific version, based on the APE file is worth considering.
Mac.
 
The Mk1 TT, has an Evap vent to atmosphere, via a gravlty valve & pressure retention valve. A2 similar vintage, so most likely very similar.
Mac.
 
PlasticMac said:
The ECU, for the twin spark engine must be quite different from the individual coil pack version. So, I'm guessing, the OBD diagnostics are different too, and the APE lable file that vcds uses for the AUA does not match it fully, hence errors.
We had a similar problem with the FSI, which is why a new, A2OC FSI, (BAD), file was recently created FOR it.
Maybe an AUA specific version, based on the APE file is worth considering.
Mac.
Click to expand...
Hi Mac

An interesting point this. It may well be that the ECU were different between the AUA and the BBY. Or they may have had different code loaded so that - for example - only the first two spark control lines were used even though there was provision for four; pure speculation on my part. When my coil pack eventually fails I will definitely have it apart to better understand how it is working. Based on the German Forum Wiki I would expect to find two distinct coils in there. I imagine it’s filled up with some sort of epoxy thou

J
 
took her out for a blast after filling up with E5 super and adding a splash of millers petrol max (on the basis that maybe she had only ever had e10 in {plus the Wynns valve treatment hasnt had mush time to do anything} ). As have only had her 3.5 weeks now and all that time has been poorly - i only did 120 miles and from filling up just - she has averaged 25mpg... [although a lot of that has been ticking over on the drive].

45 mile spirited driving around the island and i managed to squeeze 3.9litres back in so just over 50mpg = happy with that.

Tried gaffer tape on the ACF = no change - still misfires on idle
Tried AC on = no change - still misfires on idle
STFT and LTFT Trims on my AUTEL ODBII are all over the place (certainly beyond the 10% norm). I will hook up VCDS next time and log to check.

Ran really nicely on the 45 mile jaunt - only misfiring when stopped / idling for more than about 30 seconds.

New thermostat has helped with the gauge - now lifts off 60C more quickly but no effect on misfire (unlikely anyway).


interesting article here on trims - will VCDS my post cat lambda and take a look

  • A 15 percent or less change in trim and a downstream O2 above 650mV points to an ignition concern
  • A 15 percent or more change in trim and a downstream O2 under 350mV points to a lack of fuel concern


plots during travel :

1690731117589.png



flat line STFT during misfiring.

1690731737806.png
 
Hi

So good news on the thermostat, though as you say a separate concern. The consumption I have been getting over the last month with regular motorway journey has been ~55mpg dropping to 52mpg for more mixed journeys, so what you are getting is about right.

Do you know what measuring blocks your STFT and LTFT graphs are plotting or is it an aggregation from a number of them. I haven’t done it before but the VAG401 can do log capture I believe so I could give it a stab and take mine for a spin so we have some sort or comparison. (Will have to be tomorrow now I’m afraid)
 
birtyA2 said:
Hi

So good news on the thermostat, though as you say a separate concern. The consumption I have been getting over the last month with regular motorway journey has been ~55mpg dropping to 52mpg for more mixed journeys, so what you are getting is about right.

Do you know what measuring blocks your STFT and LTFT graphs are plotting or is it an aggregation from a number of them. I haven’t done it before but the VAG401 can do log capture I believe so I could give it a stab and take mine for a spin so we have some sort or comparison. (Will have to be tomorrow now I’m afraid)
Click to expand...
If you get a chance, try blanking the entry point of the Evap line into the manifold.
Mac.
 
birtyA2 said:
Hi

So good news on the thermostat, though as you say a separate concern. The consumption I have been getting over the last month with regular motorway journey has been ~55mpg dropping to 52mpg for more mixed journeys, so what you are getting is about right.

Do you know what measuring blocks your STFT and LTFT graphs are plotting or is it an aggregation from a number of them. I haven’t done it before but the VAG401 can do log capture I believe so I could give it a stab and take mine for a spin so we have some sort or comparison. (Will have to be tomorrow now I’m afraid)
Click to expand...


032 is long term - coming out at zero on my vagcom but on the driveway and misfiring
033 is short term - fluctuating mostly within 10% on vagcom on the driveeway - will take her out and log on a drive tomorrow.

An bigger ask would be to test the resistance on the pre cat lambda. I only get a reading between the red 1/2 here but elsa says it should be on 3 and 4 also (I get no reading.)

Have a busy week next week but plan to then put her into the garage and I guess this is going to be the stealership whi should have the equipment or knowledge.....

1690742080288.png
 

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tuizner said:
the evap line goes into the TB but will give it a try
Click to expand...
Ah, is it the throttle body or the spacing bit (technical term) that the throttle body sits on. As it happens I took a pic of my recent throttle body clean. Is the EVAP line the black pipe at the rear before I reseated the clip?

4C6315CF-8966-4BFF-9DBF-40610E3875BF.jpeg

Not sure how to identify cylinder number. As you stand in front of the car left to right, or the other way around? Instinctively I’m thinking left to right so I’d say the throttle body is nearest to cylinder 4
 
tuizner said:
032 is long term - coming out at zero on my vagcom but on the driveway and misfiring
033 is short term - fluctuating mostly within 10% on vagcom on the driveeway - will take her out and log on a drive tomorrow.

An bigger ask would be to test the resistance on the pre cat lambda. I only get a reading between the red 1/2 here but elsa says it should be on 3 and 4 also (I get no reading.)

Have a busy week next week but plan to then put her into the garage and I guess this is going to be the stealership whi should have the equipment or knowledge.....

View attachment 111264
Click to expand...
Sure, should be able to have a stab at that at some point early next week
 
birtyA2 said:
Ah, is it the throttle body or the spacing bit (technical term) that the throttle body sits on. As it happens I took a pic of my recent throttle body clean. Is the EVAP line the black pipe at the rear before I reseated the clip?

View attachment 111280

Not sure how to identify cylinder number. As you stand in front of the car left to right, or the other way around? Instinctively I’m thinking left to right so I’d say the throttle body is nearest to cylinder 4
Click to expand...
Yes true evap goes under TB and is that hose as you show...

Cylinders I believe are left to right as you look at them so TB is next to 4
 
tuizner said:
Yes true evap goes under TB and is that hose as you show...

Cylinders I believe are left to right as you look at them so TB is next to 4
Click to expand...
Hi

Sorry about the delay, back at work last week and very busy and I’m a bit of a woos when it comes to working on the car in the rain 🤣

So I ran the car up for 5 mins from cold and looked at measuring block 32 and 33. It was not up to temperature by the end of this but the idle revs had settled back to around 700 rpm at the end

So this is measuring block 32

AE63B8BB-6513-4F60-BC60-6CF6A10AAD77.jpeg

It didn’t move through the whole test. I have no idea if that is normal. I’ll give this a try again on an actual run with the engine fully up to temp

This is measuring block 33

38D74270-8E1C-4DE5-BBFA-E589C2AD2912.jpeg
This was more animated but this is a typical reading after about 5 mins. At the beginning I saw it hit 8% but as the engine temperature rose this is a more typical value. If I raised the revs to 1500 rpm and then let it drop to idle I could see negative values and a fair bit of fluctuation as the mixture adjusted, so would say what I was seeing was what I would expect. I did take a short video clip of this if it’s any use.

The other thing I discovered is that although the VAG401 can take recordings the file it saves makes no sense, lots of Chinese and what looks like Arabic characters in the file but nothing that makes any sense. I need to do some googling on that.

As it’s the first day here when it’s not raining and the sun is actually out I’ll see if I can get out this afternoon and make those resistance measurements on Lambda 1 for you

best wishes

J
 
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