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VCDS MAF, EGR & FUEL Temp Issues - AUDI A3 BMN 170 07'

312 Views 2 Replies 1 Participant Last post by  AshAudi8P
Hi All,

Please can someone explain my VCDS readings? They seem really strange

Bought an AUDI A3 BMN 170 07'. Got it home and smoked a bit at idle, with lumpy idle. I have VCDS so tweaked the torsion, and most of the smoke and all of the rough idle went away. However, the rear exhaust cam will not adjust below a value of 0.6l/h and my VCDs logs show weird readings compared to previous PD engines I have owned (ARL and BXE). I still get a fuel smell out the back even though no smoke and the economy seems low. Car doesn't pull in first till 3k, then pulls even more at 4k. 2-5th gear the car pulls from 2.5krevs to 3k. Brand new OEM turbo fitted a year ago, hear some whistle in 1st and 2nd but goes away after 2k revs or other gears. I had a slight whistle on ARL 150PD so assume is normal, VW/AUDI specialist said nothing of concern.

VCDS Info:

1. No engine fault codes.

2. Fuel temp only gets to 76C if I boot it and drops back to 70C but the coolant gets to 90C. Is this normal for a fuel temp sensor? Drove the car for 20mins then stopped as I couldn't get the fuel temp higher, outside air temp that day was 10C. My assumption is the fuel temp should be close to the coolant temp but may be wrong for BMN? Note the coolant temp goes to 94 if I boot it but drops back to 90-92 during normal driving.

3. MAF/EGR actual and specified logs are doing something weird, logged all gears up to 4k revs (warm engine), and all of the logs actual and specified match exactly for each time stamp. This is not normal I presume? Surely the specified and actual should not match EXACTLY? why is the ECU not throwing a MAF error? I cant think of any reason the actual would match the specified exactly. Or does the ECU overwrite actual during MAF failure? I would love to know the answer to this. I have added pictures of the MAF/EGR logs in 3rd gear up to 4k revs. Note the graph shows both specified and actual but only see one line as they are exactly the same. You will notice that at low revs and idle the actual and specified are slightly different, at idle they jump around at 450ish. As soon as the load increases they match.

4. Lastly the EGR, the duty stays at 0% no matter what, idle, acceleration, or steady revs. It flicks to 30%ish when revs drop quickly between gears, which seems unusual. I cleaned the EGR to ensure it wasn't sticking last night with no change. I also cant perform a basic setting of the EGR, I tried but the revs don't rise to 1400rpm and it says abort. What is going wrong here? I assume the basic settings on the EGR is a test, hence why I did it. I turn the ignition and engine on, turn the test on and hold the brake and accelerator, nothing happens and it says abort.

Never had a VCD read with so many weird issues like the ECU is messed up or it's been mapped wrong? Didn't think it had been mapped?

Really could do with some knowledge.

Thanks in advance.


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I just tried to test the EGR in the output test with EGR off the car (plugged in) but there is no option to test it. Why do I not have this option? So instead I ran basic settings test, and the car revved to 3000k then back down to 1400, then the egr value went up and down more the 100mg/st which I assume means the EGR is working. The duty cycle went to 40% then back to 0%, stating 0% is closed. However, when I drive the car in all gears at all revs ranges the egr stays at 0%?

I am really stuck with what this car is doing. To add the Lamba/o2 sensor starts in range, as it warms up it goes above range, as in above 1.0-2.0 and sits at 5-6.

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