Car was running great, all of sudden started running rough. Engine light on, got it home on a scanner has 8 codes P0174, P0102, P0112, P1642, P0301, P0304, P1316, P1111.
WOW all of these just came up at the same time. First thing I did is replaced the plugs for the misfire. Didn't work. Swapped the coil packs on cyl 1 and 4 with other cyl's still
getting same misfire on P0301 and P0304. I swapped the mas air flow just to see what would happen, nothing. I think my 2002 has cyl 1 and 4 on the same bank so trying to think
of what could make the outer cyl's misfire. Any ideas?

 

Double check you connections in the boot of the coil pack for proper seating and be sure your plugs are properly gapped (don't trust pregaps). Do you have a noid kit (a kit to test your leads to your coils)?

Your other codes were triggered because of the dead cylinders pouring straight gas out the exhaust, I would not concern yourself with those until you get your coil pack issue resolved.

 

My first question is have you cleared all of the codes, driven for awhile and the rechecked? If so, is the P0301 and P0304 the new codes?
Cylinder 1 and cylinder 4 are both on the passenger side. #1 being the front and #4 being the rear.
If you have swapped out the plugs and the coils without change, then my next step would be to pull coil and plugs from #1 and #4 and do a compression test.
If compression is good my next step would be considering replacing the injectors for those cylinders.

Your initial codes were indicating excessive misfire and lean conditions for on the right bank.

 

Oh boy, getting good compression on both cyl's 120 psi on each. The plugs are new on all cyl's NGK BKR6EIX came out of box gaped at .032 re-gaped to .050 using proper gap tool.
Well I guess next step is injectors? That's gonna be some work. thanks for info.

 

Just to confuse the issue, I had the P0301/0304 lean condition codes as a warning when my fuel pump was showing signs of failing. Over a several weeks the condition became worse with the engine struggling to run one minute, and running fine the next, A replacement fuel pump was the cure.

Not sure if this would apply to an XJR due to them having two fuel pumps?

 

You are using wrong spark plugs (wrong heat rating) and too large gap. All engines from the year 2000 should use PFR5G-11E (or BKR5EIX) with a gap of 1.1 mm or .040 in. Perhaps putting in correct spark plugs will cure the problem. Otherwise, the general rule is that the gap on new Iridium plugs should not be tempered with.

 

Dont erase code P1111 if erased you will have to do a drive cycle test. If I understand, you swapped known good coils to 1 and 4? still got the same codes? I think you should erase all the codes except for P1111 road test to see if the misfire changed to a different cylinder. Would not hurt to run a fuel pressure test as well.

 

Get New set of spark plugs if not solved then you may need change coil new set high quality ignition coil is about 99$ im using one in my car it works perfect