2012 audi a4 quatro, cylinder 2 misfires, replaced cylinder 2 coil, replaced all spark plugs, 2nd cylinder fuel injector, cleaned carbon off the valves, replaced oil separator assembly, compression test reveals cylinder 2 at 130 vs 1 3 and 4 at 170, misfires at idle only, Please help
My car has 71500 miles.
My car has an automatic transmission.
The variance in cylinder compression you are reporting exceeds that allowed in the Factory Service Manual. Put oil in the No. 2 cylinder to see if compression rises appreciably and you can then rule in or out leaks past the rings (the oil has the effect of sealing the rings). If compression is not higher with oil, the head gasket and/or valves are leaking and that may be a part cause of the misfiring. If those components are leaking, the engine will have to be repaired. There is always a possibility of an electrical fault in the injector circuit, so you can evaluate that and, as well, look at the secondary firing pattern in cylinder two which will provide clues as to what exactly is going on in that cylinder. If you desire a more conclusive diagnostic, please request a misfiring diagnostic and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
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