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FIrst have them do a compression test on the engine. Cylinder 5 is in the back so the intake will need to be removed. If the compression test is good then have them swap out an injector with another cylinder. If the code follows to that other cylinder it's an injector. If the compression is low only on cylinder 5 then you most likely have a burnt valve. If it is low on all cylinders then the timing may have jumped.
I went in for echeck in engine light. This is what jaguar performed and my engine idled low. Here is what has been done so by tech. this is what is on my jaguar invoice. cylinder 5 misfires under intake manifold, replaced 3 sparks plugs and ignition coils under intake. vehicle still misfiring after replacing spark plugs and coils. Performed compression test. cylinder leak down test-no leaks. swapped fuel injections from bank to bank,performed exhaust back pressure test. checked ECM inputs/outputs. performed vacuum leak test. checked for blown head gasket. Found engine wiring harness corroded and was replaced. performed cylinder leak test and compression test AGAIN. cylinder leak was 5% and under for all cylinders. compression between 160-165 on all cylinders. performed fuse test numerous times,performed smoke test on engine to verify no vacuum leaks. swapped front 02 sensors from bank 1 to bank 2 to verify.02 sensor operation. swapped mass air sensor. ECM to verify operation. FOUND bank 1running rich and bank 2 running lean indicating that timing is off. What does the problem sound like it could be