I have an 07 XKR. I developed a progressively worsening p0300 and p0316 and codes for misfires on 2, 4, 6, and occasionally 8 over a 3 day period. I limped home the last 1/4 mile at sbout 5mph at idle. I had replaced all plugs about 3 months and 2k miles prior so I was in there with all the brittle plastics etc. I did gap plugs and torqued. Battery is new and holds 12.8 at rest. I've switched coils from one side to the other. I changed oil and verified VVT volts and ohms. I checked electrical specs on O2 sensors and upstream was a bit suspect so I replaced all 4 (just cuz). I had received a p0430 5000 miles or more back and it would rarely show and I could clear it with Torque Pro. It did go away after plugs...??? I've hooked up JLR SDD v136 and get wildly fluctuating fuel trims on bank 2. I pulled air filter and it was 'normal' dirty and replaced. While there cleaned MAF sensor. I know that it's gotta be ignition, air or fuel. Absolutely no codes from Bank 1. While I was doing O2 sensors I did the bang test on the cats and the drivers sound more dull thud then drivers. O2 sensors now read pretty good, consistent voltages, but I can't really get (or dare) to run long enough to be sure alls cool. I am suspecting CAT or a vacuum leak on some bank2 specific vac line. Anybody got any advice?

Thanks so much in advance.
Bil

 

Original CATS? How many miles on the car?
Swap the mafs side to side?

The workshop manual provides good insight on the magic of fuel/air ratios and all of the components measured by the ecu in calculating the approach. All I'm saying is don't rule out clogged cats.