Hi All,
I'm in need of some direction. I got my 2006 XK8 about 6 months ago (147K miles), where she had been neglected for quite some time. In trying to pass VA Emissions Testing, I'm wokring my way through the codes, and the current misfires have me stumped.
The codes I get reliably are :
0300 random, multiple cylinder misfires
0306 number 6 cylinder (the most frequent culprit)
1316 fuel injector code
and now I get 0430 ban4 2 catalytic converter operating below threshold.
All of this is in addition to that gem P1000 (the engine tests have not all reset)

I'm not worried about P1000, or even 0430 at this point. I THINK what is happening, is #6 cylinder is misfiring causing the 0300 and the 1316. It's done this enough to goober up the downstream O2 sensor, causing the 0430.
I'm stumped how to fix this misfire. Here's what I've done:
All new breather from the aif filter box through the throttlebody. No leaks there.
MAde a new PCV Breather Tube. It, too, does not leak.
New NGK spark plugs. I've swapped plugs into and from #6 cyl, but it still misfires. I do not think it's the plug.
New Jaguar brand ignition coils. I've swapped the coils around MULTIPLE times and still #6 misfires. I do not think it's the coils.
I added a can og BG44k to the tank and drove it like I stole it. Still misfire and engine codes
Changed out the fuel filter. Old one was gross. New one is new. Still those 4 codes.

I'm fairly handy and have tools and a space to work. I'm just notsure which direction to take this in next. Any suggestions? It'sgetting to be convertible weather here, and I'd love to take her out... if I can pass emissions and get a real tag for her!
Thank you in advance for any advice you can offer. This forum has been a HUGE help already!

 

Three things to check:

1. Battery voltage across the terminals when checked with a voltmeter
2. Fuel pressure should be 3.3 bar
3. Compression test

If battery voltage is at least 12.6 volts with the ignition in the OFF position, check the fuel pressure.

The fuel injector for that cylinder may not be functioning, or there is damage to the wiring loom.

If the fuel injector is functioning correctly, perform a compression test on the subject cylinder as loss of compression can cause a misfire.

When DTC P0430 appears, it means the catalyst is damaged and must be replaced on Bank2. Resist the temptation to start replacing oxygen sensors as that isn't going to fix the problem.

 

Thank you!
Battery was 12.57 volts, pretty consistently.
Looking at the Fuel Rail Pressure, it was 55 psi, so I think that should be okay. The suggested rate was 3.3 bar (about 48 psi).
Compression test: Here's the rub. I'm new to comprssion tests, and I got all kinds of readings, from 85psi to 180 psi. The number 6 cylinder, which consistently gives misfire codes, was consistently low, but they were all over.
I put a tsp of oil into the spark plug hole and ran the test again. It came up about 10 psi higher, so... piston rings?
Have the cylinders bored and new pistons and rings?
Thank you again. I think we can cross off fuel pump... but I'm not positive about the battery...

 

Oh, I got a new OBDII reader, the BAFX model from Amazon:
I got Torque Pro and am starting to play with that too.

 

Fuel pressure at 3.3 bar is good. Battery is marginal. If there is compression showing for that cylinder, there should be no need to replace internal engine parts.

If you haven't done so, check the wiring loom and connector to the coil unit and injector for damage or poor connections.

 

Will do. Thank you!

 

Okay! It's been a awhile, but Mick Jaguar is back! He spent so long in the garage, my family is calling it a "Housecat". Grrrrr...
After a year, I've finally passed Emissions and obtained registration and a tag.

I'm not entirely sure which voodoo my latest mechanic aplied, but a new Catalytic Converter seems to have solved my engine misfire problems.
If anyone's ever tried to buy a new Catalytic converter, they are like gold... literally! I got once off Ebay from DEC, custom made for my baby. It was about $315, and the dealer charged bout that much again to install it. (Worth it!) Be sure, if you swap your Cat Converter, to get the old one back! They are full of precious metals, and can be sold online. I asked my mech to give me the old one, but he forgot and sold it to a scrapper. He was kind enough to pay me what the scrapper was going to receive for it- about $250! This helps keep the wife a LITTLE bit happier.
I guess I need to drop the top and take her out for Ice Cream and a run down Skyline Drive in the Shenandoahs.

Thank you everyone for the advice and tips!! I'm VERY excited to finally be able to drive my cat legally!!