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Audi0405
Audi0405, Technician
Category: Audi
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Experience:  10 years in Vw and Audi Field
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Audi A4 Quattro: I have a 98.5 Audi a4 2.8. I have been getting

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I have a 98.5 Audi a4 2.8. I have been getting a bad misfire and I'm stumped. The engine misfires at idle but is much worse under load. the car smooths out pretty well at highway speeds and if i feather the throttle really gently. Initially I got random/multiple misfire and misfire cyl 2 and 5. I changed the plugs with new NGK coppers and all new Bosch plug wires. The misfire went away for about 4 days then came back. I pulled codes again and it showed random/multiple, and misfire cyl 2 and 6. I put in new cats and a new fuel filter which made no difference. I put a can of injector cleaner in and I'm working my way through the tank of gas. Cleared codes and it showed random/multiple misfire and misfire cyl 2. I replaced the cyl 2 injector and cleaned the rest of the injectors, put new seals on all 6, and put replaced all vacuum lines. Misfire is still the same and throwing random/multiple and cyl2 misfire. I am replacing the coil packs today (I haven't yet because it has never shown misfire for the other cylinder on the cyl 2 coil pack).

So, I am trying the coil packs today, but if that doesn't work I'm at a loss. Any other ideas?
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Do you know what the compression readings are on that cylinder yet?
Customer: replied 3 years ago.
No, I haven't done a compression test yet. What are you thinking?
More then likely
It's a coil issue but is the coil does not fix it you will need to check compression in that cylinder to make sure
It's close to the other cylinders and its not low , is compression checks out you may have too much carbon build up in the intake valves causing the cold start misfire and this will require intake removal to clean them up . I hope this helps

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Customer: replied 3 years ago.
Got it, thanks! I will check compression next. On a side note, the misfire actually gets worse when the car heats up and is better on initial cold start. Does that make a difference?
No but it sounds to me like a coil issue .

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