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D2 - Engine Bay Everything under the bonnet |
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Thread Tools | Display Modes |
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I don't think it will be ignition amplifier, faulty ignition amplifier normally result in misfire fault codes and usually only 1 or 2 cylinders not all 4, addition to this each ignition amplifier controls 3 cylinders on each side, not 1 side each. If I remember correctly 1 is for cylinders 1,4,6 and 7 and the other one for 2,3,5&8.
Now to the knock control fault codes, first lets understand how the system work. There is a knock sensor on each side of engine which measures 'knock' or speed and violence of the explosions in the cylinders. If the combustion is too fast/sharp ECU retards ignition timing a bit at the time until combustion speed is normal. If it gets to the point where it has retarded the ignition timing as far as it can and it's still knocking it will throw up error code. The reasons why the knock occurs are: 1. Too little fuel (or too much air if you look at it the other way) 2. Poor quality or octane fuel 3. Overheating 4. Large amount of carbon buildup in combustion camera. 5. Faulty knock sensor 6. problem in wiring 7. Or it could be false alarm if you have loose bolt, nut or whatever knocking on the engine. It only shows the error codes for 1 bank of cylinders but it could be an issue that affects both banks but because of slight differences one might be just over the limit to bring up fault codes and the other one just under. Considering that the car stalls in the short while after being started I would look at the fuel supply first- amount of fuel in the tank,fuel pump, filter, pressure regulator, relay. Have a look at measuring blocks 13,14,15 and 16 on VCDS to see if ignition timing gets retarded for one bank or both, that will show you if you have issue that affects both banks or only one. And then you can explore options depending if it's 1 bank or both.
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Currently 8less 2011 Q7 S Line 3.0TDI, 2016 Tesla Model S 90D 8 history: 2006 A8 Sport 4.2TDI quattro SOLD, 1997 S8, reached end of life with gearbox failure |
#2
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Thanks guys. I did swap the ignition control units - the car would run as rough as before and I was not able to tell which cylinders were affected after swapping. Error codes are now no longer appearing after clearing them but the car still runs rough and dies. If I leave only one unit connected at a time, car will only start with one of them so my idea was that it might be actually it.
Having also posted on Polish A8 forum, http://www.a8team.pl/, guys in there are saying this is a fuel pump problem and it should be replaced. Could that be the case? Will check the measuring blocks later on today. Cheers. Tom
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Tom VW SCIROCCO GT2 '92 |150BHP -LHD VW SCIROCCO GTX '84 |150BHP -RHD VW SCIROCCO MK1 '78 | ??BHP -LHD PORSCHE 924 '81 PORSCHE 944 '84 Audi A8 4.2 Quattro PF |
#3
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On another note, if this proves to be a fuel pump problem, had anyone used aftermarket replacements and can comment on them?
Cost on ebay: replacement pump (aftermarket) ca £40 replacement pump (eurocarparts) ca £95 replacement pump (genuine VDO) £125 Costs on polish 'ebay' allegro replacement fuel pump (aftermarket) ca £30 replacement fuel pump (genuine VDO) ca £90 Thanks, Tom
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Tom VW SCIROCCO GT2 '92 |150BHP -LHD VW SCIROCCO GTX '84 |150BHP -RHD VW SCIROCCO MK1 '78 | ??BHP -LHD PORSCHE 924 '81 PORSCHE 944 '84 Audi A8 4.2 Quattro PF |
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