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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 21993
Experience:  BEng hons Mech engineering, in auto industry 22 years
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A8 4.2 quattro 1998 abz engine, I washed the went to start

Customer Question

Hi a8 4.2 quattro 1998 abz engine, I washed the went to start it the cat light came on
And it then developed a misfire, took it out thinking it would clear but it began to vibrate
Violently so returned and parked up, not tried it today yet, is there anything obvious it
Has been superb until this, I've only had it a week!
Regards bigal1066
Submitted: 4 years ago.
Category: Audi
Expert:  Matt replied 4 years ago.
Hello

when you washed it did you wash the engine at all?
Customer: replied 4 years ago.

Hi matt, no I did not wash the engine bay at all, its the only thing I did to it since parking up last Sunday until then it was running perfectly, since posting my question I have bought a set of ngk iridium plugs which I intend to fit over the weekend, please feel free to offer any suggestions you may have

Regards. Alan

Expert:  Matt replied 4 years ago.
Hello alan
Some new plugs is a good start, these cars are also prone to coil issues so try spraying them with some water with the engine running
If you get any sparking or crackling replace that coil
Customer: replied 4 years ago.

Hi Mat, thanks for that a good tip, I also have one of those scan tools, could you tell me the number sequence of the cylinders? Am I right in thinking that stand at the front of the car the left hand bank is numbered 1 to 4 and right hand side bank is numbered 5 to 8 from the front

Regards

Alan

Expert:  Matt replied 4 years ago.
Hello Alan

this should help

graphic
Customer: replied 4 years ago.
Hi Mat, changed the plugs but still misfiring scan code 66684. 01/03 does this mean cylinders 1 & 3 are at fault? do you suspect coil packs?
Regards. Alan
Expert:  Matt replied 4 years ago.
Hello Alan

audi coil packs are notorious for misfire issues so that woudl be my 1st instinct

however this ECU on these cars are also prone to issues so it may be worth getting the ECU checked over as this will be a lot cheaper than replacement

http://www.the-ecu-doctor.co.uk/

http://www.bba-reman.com/