Hello. My wife's 04 XJ8 has been a very reliable car. Today however, when she backed out of a parking space the engine went into restricted performance mode and ran roughly.

When I got home from work I pulled P300, P301, P303, p305, P1313 and p1316 codes.

I took out the number one cylinder coil and plug; the plug looks ok. Going forward with the diagnosis my SOP (standard operating procedure) would be to move coils/plugs around to determine the cause, but with three cylinders that are right next to each other misfiring it seems too coincidental to be plugs or coils.

Could the PCV valve that sits atop those cylinders be causing the problem? There is a light oil residue in that general area (beneath the PCV).

Thanks,
Jeff

 

I removed the PCV to inspect it. It does not rattle when shaken, and air goes through freely in both directions. I filled it with carb cleaner several times and drained tons of dirt out, but it still doesn't rattle and air goes through easily in both directions.

I am no expert (understatement), but it seems the valve is shot?

Would this cause a massive vacuum leak in this area possibly accounting for those three cylinders misfiring?

 

Hi Jeff,

It definitely sounds as though your PCV valve is stuck open, which can cause misfires at idle. The P1313 code indicates that the misfire rate could lead to catalyst damage, and the P1316 code indicates the possibility of excessive emissions. At the link below you can download the full Jaguar X350 DTC Summaries Manual to see the lists of other possible causes of your codes:

https://www.google.com/url?sa=t&rct=...03388427,d.cWw

Cheers,

Don

 

Thanks Don.

I appreciate you helping me narrow down my diagnosis. I just ordered a new PCV from Amazon which will arrive Wednesday morning.

When I removed the plugs I discovered they are NGK 7090, which are platinum if I'm not mistaken. Tomorrow I am going to pick up 8 new NGK 5464 (BKR5EIX-11) iridium plugs to replace the old ones.

I really hope this solves the problem.

Thanks again.

P.S.-- I asked my wife and she said it ran fine at speed, but the misfiring occurred every time the car returned to idle. Sounds like a little more confirmation.

 

Hi Jeff,

I haven't looked up the NGK 5464 plug - is it an upgrade of some sort? According to the Workshop Manual, the N/A cars use the same plug as the S/C cars, NGK IFR-5N10 Laser Iridium (7866), which is what I installed in our '04 XJR with good results. The Jaguar part number is AJ8 4575. Here's the section from the Workshop Manual:




What is the difference in the 5464 plug?

Cheers,

Don

 

Good morning Don,

According to the NGK website there are three options for the x350, with the primary difference being lifespan. I put the 7866 plugs in my x308 because I drive it a LOT. My wife does not drive nearly so many miles.

The 5464 are still iridium but even with their reduced lifespan it would take her years to wear them out. I would prefer to just change them again in 2 to 3 years and get them at half the price. All that said, the biggest motivation is that the 7866 plugs are special order around here whereas the 5464 are in stock at both of the local parts stores I frequent.

I am very open to having my mind changed however, I have not bought them yet.

 

Hi Jeff,

I do remember now that we had some discussion on this topic - I think it was Box who recommended the 5464 plug. I recall that one of the NGK websites (how many are there???) indicates that the 5464 is actually a better-performing plug than the 7866, but with a shorter lifespan.

A quick search didn't turn up the NGK website that had performance ratings, but I did find one that shows not just 3 but 5 plug options for the X350:

NGK Automotive OE Replacement Parts on NGK.com

The options NGK gives, from least to most expensive, are 2382,6953, 7090, 5464, and the OE plug, 7866.

One thing I recall from the previous discussion was that NGK recommends a different gap for the 5464 compared to the 7866. The site linked above shows the OE gap as 1.0 mm (0.039 in.), but if you click on the SPECS links you'll find that NGK recommends a 1.0 mm gap for the 7866 and 7090, but a 1.1 mm gap (0.043 in.) for the 5464, 6953 and 2382:

7866 Specs:
NGK 7866 IFR5N-10 Iridium Spark Plug

5464 Specs:
NGK 5464 BKR5EIX-11 Iridium Spark Plug

That raises the question of what gap should be used for the 5464 in an X350. I don't know the answer, but since NGK obviously has a reason for recommending a larger gap for the 5464, I would lean toward their recommendation rather than the Jaguar spec.

I'll be curious to hear if you can discern any difference in performance with the 5464s. I personally wouldn't mind changing the plugs every 40K-50K if the performance and/or fuel economy improved.

Cheers,

Don

 

The PCV valve won't rattle like the old style ones. If you have oil residue on the cam cover that indicates the o-ring is seeping. They are oddball size metric 2.65 Cross-Section, 2x 16mm and 2x 14 mm ID on the PCV side.

I think the proximity of the PCV valve to the misfiring cylinders is a red herring. The PCV pulls vacuum into the throttle body, so a leak would cause a lean condition on all cylinders (or one bank). I would look closer at the harness feeding the related coil packs, as that might be more relevant to a group of coils not firing.

 

The rattle test aside, the fact that the valve allows completely unrestricted airflow in both directions concerns me. I am standing in the garage waiting on UPS now, so hopefully I can find out if the PCV valve is the problem very soon.

I am planning to hard reset the battery, re-install the coils (took them off to check for oil and clean the connections), and hook up my fuel trim monitor. I hope to have answers soon one way or the other.

Thanks

Edit - I forgot we have plans with friends this afternoon. I have to leave before UPS gets here. BUMMER.

 

Back from our friends house...

The last time I started the car (day before yesterday) it ran very rough and began misfiring immediately upon starting the engine. The misfiring was continuous at idle and only seemed to stop at higher rpm.

I bolted on the new PCV valve that was waiting on my front porch. I didn't do a hard reset, I took the lazy way out and just erased the codes with my scanner. The car started easily and ran smooth with no indication of misfiring. I went for a 10 mile drive at varying speeds and pulled it back into the garage, still running smooth with no codes. I plugged in the scanner and only got p1000, which I had expected since I cleared the computer.

I have worked on cars enough to know better than do a victory dance. It certainly "appears" as though the PCV valve was the problem, and that the new one "fixed" the problem. I am also aware of the possibility that I may have moved a wire or somehow inadvertently improved a connection that solved the problem. If my wife drives it for a few days with no recurrence, then and ONLY then will I perhaps accept that the cause of the misfiring was in fact the PCV valve.

Thanks for the help.

 

Eight days and a couple hundred miles later; her car still runs good with no misfiring or codes.

yay

 

Is this the PCV valve you are reffering to?




I have same issue and I am going to replace mine just in case its the same solution.

ordered mine

 

Yes, that looks like the same part.

In fact, when I followed the link you posted for the part it turns out that's the exact thing I ordered. The Amazon page says "You purchased this item on December 7, 2015".

 

https://www.jaguarforums.com/forum/x...2/#post1430655

I just replaced my PCV. I had the same codes and so far it has not popped a code since.

Pretty happy, the car drives really well, its a amazing car.

https://www.jaguarforums.com/forum/x...2/#post1430504

 

I do love a happy ending.