Q: cylinder 3 and 4 misfire

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It all started with overheating, then we discovered the cat behind the turbo on the drivers side is blocked. We solved that, it wasn't still working well then I opened it to check for timming issues and I noticed the passenger side bank exuast and intake was off a bit, I then set it back cos am also a mechanic. From time to time I do hear the cam adjusters hitting the cylinder head covers but didn't want to think it could be the cause. Now it's worse, the engine is no longer working fine and cylinder 3 and 4 are not firing at all, even swapped the ignition coils but still the same. Now am guessing the igniters on the air box or cam adjusters making the engine timing shift. Secondly, if the notch and arrow pointing the direction of timing on the cams are slightly off, can it cause a big drop in power to the extent of not firing plugs 3 and 4. Thank you, Martin. My email -martospliff@gmail.com, Audi 2.7t 2000 model year

Hi there. Check the spark plugs to see if they have burn spots on them. Switch them out with cylinders that are firing. If the other cylinders do not fire now, then the spark plugs need replaced. If the same cylinders 3 and 4 are still misfiring, then there could be a burned valve. Check the compression on the two cylinders and compare them to the other cylinders. If they are both low, then you will need to perform a leak down test (which requires a source of compressed air like an air compressor or something). If the compression on the cylinders is good and a leak down test passes, then there could be an issue with the fuel injectors not firing on those cylinders. If you need further assistance with your engine misfiring, then seek out a professional, such as one from Your Mechanic, to help you.

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