I'm getting restricted performance flashes at around 2k rpm while decelerating, occasional CEL with misfire or coil codes in bank 1 only (1,4,6,7 coil set). Long term trims are right around zero and short term trims are no more than -6% when CEL comes on. Both bank 1&2 fuel trims are exactly the same (less than 1% deviation). There is no perceptible loss of performance or idle smoothness. CEL goes away after a few starts. Only happens with engine warmed up and after many miles driven usually 20+. 87,000 miles on odometer.

Sparkplugs and coils are new and I've moved them around so it's not that. Tested coil wiring and it all tests good. Fuel trims suggest no problem with fuel delivery...? (usually cylinder 6 flags first... One bad or leaking injector? Sometimes cylinder 4 flags first, both in same bank 1 though). No fuel smell from exhaust.

In really thinking my bank 1 upstream oxygen sensor is the culprit. No flags from the sensor but that wouldn't be the first time a Jaguar threw codes that didn't exactly match the problem. The fuel trims are what lead me to think thusly. The banks match and 6% is still in the good range for short term, right?

I'd love to hear what ya'll have to say before I spend 200 bucks for one sensor.

 

You have misfire DTCs for BOTH BANKS.

#1 and #7 are on bank one.
#4 and #6 are on bank two.

 

I understand that 1 & 7 are bank 2 but the only cylinders that show up on DTCs are 4 & 6.

 

As mentioned by motorcarman, bank 1 is 1,3,5,7 and bank 2 is 2,4,6,8.

Have you tried testing injectors 4 & 6, both the wiring to them and the injectors themselves? Swopping them out?

My injectors numbered 7 & 8 became somewhat intermittent before (this at different times) failing altogether?

 

You stated you have DTCs for Cylinders 1,4,6,7 but they are all on bank 1?

I'm confused.

 

What prompted you to change all of the spark plugs and coil packs in the first place? Regarding the injectors, they can easily be checked in place with a mechanic's stethoscope.

 

OK SORRY. I see now that I made a few mistakes in the descriptions in my posts. I mistakenly stated that my problem was bank 1, it is actually bank 2. When I mentioned cylinders 1,4,6,7 I was trying to communicate that I understood that those 4 cylinders make up one of the two electronic circuits. So if you guys don't mind I'd like to repost my original post with the corrections made.

 

HERE IS MY ORIGINAL POST CORRECTED

I'm getting restricted performance flashes at around 2k rpm while decelerating, occasional CEL with misfire or coil codes in bank 2 only (cylinders 4 & 6). Long term trims are right around zero and short term trims are no more than -6% when CEL comes on. Both bank 1&2 fuel trims are exactly the same (less than 1% deviation). There is no perceptible loss of performance or idle smoothness. CEL goes away after a few starts. Only happens with engine warmed up and after many miles driven usually 20+. 87,000 miles on odometer.

Sparkplugs and coils are new-ish (not originals) and I've moved them around so it's not that. Tested coil wiring and it all tests good. Fuel trims suggest no problem with fuel delivery...? (usually cylinder 6 flags first... One bad or leaking injector? Sometimes cylinder 4 flags first, both in same bank 2 though). No fuel smell from exhaust.

I'm really thinking my bank 2 upstream oxygen sensor is the culprit. No DTC from the oxygen sensor but that wouldn't be the first time a Jaguar threw codes that didn't exactly match the problem. The fuel trims are what lead me to think thusly. The banks match and 6% is still in the good range for short term, right?

I'd love to hear what ya'll have to say before I spend 200 bucks for one sensor.

I'M ALSO POSTING THIS DIAGRAM, THIS IS MY UNDERSTANDING OF HOW THE CYLINDERS ARE DIVIDED ELECTRONICALLY.



THANK YOU FOR HAVING TAKEN THE TIME TO ANSWER AND FOR YOUR PATIENCE WHILE I SORTED OUT THE MISTAKES I MADE.

 

I replaced the sparkplugs and coils when the coils started failing, they were the originals. I replaced the sparkplugs with the correct NGK IFR5N10 and the new coils are Bremi. It had nothing to do with the problem I'm having now. The reason why I don't think it's the injectors is because my idle is smooth and I'm getting no perceptible misfiring. When the restricted performance light flashes it only flashes for a second, then stops, right around 2k rpm but there is no loss of performance whatsoever.

 

Usually misfires cannot be felt but when they are it's because they're really bad.

The PCM can and usually does detect misfires which you cannot feel.

With the right plugs I'd suspect the coils, whether new or not.

 

One thing you cannot hear, when listening to injectors, is if there is a slight leak. Fuel is cut off when decelerating with foot completely off throttle. A leak will possibly be recorded as a misfire since the leaking injectors may produce power and throw off the cam timing signal that indicates misfire.
Try deceleration with a tiny bit of throttle and see if you get the same fault.

 

Have had something similar on a 1997 XK8. Faults on coils 2,3,5 and 8 (two on each bank) but also had fault: P1368 Ignition group 2 defective. Not sure how this problem started as I don't know the history of the car but likely with faults on one coil.
Turned out to be leaking capacitor in the ECM and made some damage inside the computer.





Have replaced XK8 computers in the past, haven't done it (yet) on a X350 but faults looks similar. Not saying this is your problem but keep it in mind as it looks like your ignition group 1 is failing.

 

delete

 

I know with a v8 this is probably more true than a 4cyl, and I believe the electronics are better than my increasingly tired senses. For now I am trusting the codes and looking for issues. I haven't been real happy with the Bremi coils, I've had to replace 2 of them since buying them new (in 2019). I will probably do some more coil swapping.

 

Interesting... The only cylinder that ever records a misfire is cyl 6 (P0306), the other codes are always the P0351, P0354, P0356, (funny it never includes cyl 7). I am gonna try what you suggest. I have noticed timing advance as high as 43 degrees when the code flags, does this tell you anything?

 

I have no problem cracking open a module and sniffing out bad caps! Actually a pretty easy possibility to eliminate. Might give it a try.

 

did you check for any vacuum leaks

 

Hey, I've only done visual, cursory checks for vacuum leaks. Spraying carb cleaner doesn't seem to do much on these jags. Most of the tough vacuum problems seem to be coming from the intake manifold, so I might end up doing a smoke test.

 

I hope you were able to read the corrections I made to the bank/cyl confusion. I had a significant deterioration of performance just a couple days ago. The car is no longer driveable. Is that how your car became when your injector(s) finally went all the way bad? Mine is acting almost exactly like when a couple of coils went bad a couple years ago. The car jerks and restricted performance light stays on, along with CEL flashing and car jerking and transmission slamming out and into gear. Would love you hear of you experience.

 

Hi Victor,

I had a similar issue some time ago now. I was getting misfires on one cylinder and they got worse and worse, car was juddering and lurching and ended up flashing the CEL with misfire codes. My problem was a failing injector. They seem to start to fail and cause intermittent misfires and mine did not throw any fault codes for the actual injector until it finally threw an open circuit fault.

I then had the same symptoms on another cylinder and installing a new injector fixed that problem as well.

You can firstly test the OHMs of the injector to see if you are getting the correct readings. You should get a reading of around 14.9 and they should be a steady and constant reading. If you are getting fluctuating OHMs readings when you test for a period of time or you get no readings at all or you get a reading of 1 (meaning open circuit) then you have a faulty or failing injector on that cylinder.

I helped EsRay in this thread (post 2 and 6) which I described how to test the injector on the cylinder that is reporting the fault.

Thanks,

Chris