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mateusz1611
9th March, 2016, 08:43 PM
Hello
I have a problem with Audi S4 B5. My friend bought this car few months ago with modified software 1.1bar. Everything was ok about 5 months but 2 weeks ago car started jerking like misfire between 2800 - 5000 rpm. In ecu no faults so i made logs all parameters. Boost specified and actual perfect 1.1 bar, cam shaft regulation ok, lambda rich, injection timing smooth max 23ms. We replaced new MAF, plugs, coils, injectors, DV, but car have big timing retardation, 6 degrees 3000 rpm and 12 degrees 6000 rpm. I read ecu and software looks ok. I made second software with 0.9 bar and problem is but a little less I tried EGT OFF but still the same. So I wrote ori and car is driving normal now, no jerking but still is timing retardation about 7 degrees. I tried third software and car starts jerking when boost achieve 0.85 bar. Car doesn't have catalysts, has bigger IC.The rest of the parts are stock. I don't have idea where is problem. I will be very grateful for any help

gad3n
10th March, 2016, 07:42 PM
i had similar issues ... turned out faulty fuel pump

mateusz1611
10th March, 2016, 10:04 PM
fuel pump is new, fuel pressure ok

bobolin4o
11th March, 2016, 06:47 AM
Bad fuel, small air leak between turbo and inlet, knock sensor (wrong signal, mechanical issue - some noise from camshafts, valves, etc)... low power supply for coils, injectors...

CustomCars
11th March, 2016, 08:33 AM
bobolino4o give you good tips.
Please check knock sensor physical and on diagnosis, clean halla sensor


Ignition causes incorrect behavior

mateusz1611
11th March, 2016, 09:59 AM
Thanks for response.
Mechanically engine works ok, no sound from heads (cam shaft regulation etc.). This ecu (551c) doesn't have possibility diagnose misfire but no have any faults now. But like You said I am going to check knock sensors, hall and power supply on coils.

oem
14th March, 2016, 08:34 AM
Also very rich or very lean mixture :), very small spark gap, little ignition advance also provide missfire on WOT...

But... i read now that you have big retarding. Check fuel mixture first!, then check for oil leak in cilynder. Check for leakage injector. Loggin live data and check wich cylidner retarded. All, random, or always the same? Check tighten knock sensor!