Hello,

I'm taking my 2005 XJ8 Vanden Plas in to the mechanic for regular service in a couple days, but just today something cropped up and so for merely temporary slight peace of mind, I thought I'd come to the greatest aggregated compendium of Jag knowledge for some harmless theoretical troubleshooting.

Today, while pulling to a stop at a light in the extremely hot Texas weather, my engine's traditional effortless purr started slightly laboring. Nothing major, but a slight vibration when stopped. Seemed to run just fine when in motion, but when at stop, it felt slightly labored.

Nothing leaking. No engine light. No message center warnings..But a definitive yet very small vibration, and noticeable but not large laboring.

I know this is all about as vague as can be, but any thoughts?

Tom from Dallas

 

Try scanning it and see if anything comes up.

 

meriorn1,

Excellent suggestion, but I don't have my own scanner--although I think this is probably reason #1 I should get one--and all the various places I could just have it scanned had closed for the night.

Tomorrow, I think that's probably on the docket.

Much appreciated!

 

How old are plugs? air filter? fuel filter? Have you tried any fuel injection cleaner or a different tank of gas? I think it is just some dirt in the fuel system. A fuel injection cleaner (I use Rislone BTW at least once a year) will most likely fix the problem along with a fresh tank of premium gasoline.

 

mkoko,

Hey, Indianapolis! My hometown!

Always use premium gas, just filled up on Friday. And, I regularly use some fuel injection cleaner.

This morning, I'm going to get a code reader and see if that doesn't reveal something.

I purchased the car in April, and I had the plugs replaced. The air filter was just replaced in April. No idea on the fuel filter..

Thank you for the response!

 

Something that I need to mention. The fuel filter is like $15 and is 30 mins DIY job. On a a 15+ yr old car; it can't hurt to clean it. I am sure the old one is dirty and probably showing some rust. Just get a good jack, gloves, and eye protection.

This is one of those jobs that any mechanic can do. The shop doesn't have to be a jag/import specialist. It is literally 2 circular bolts/clamps and one torx screw IIRC. I would take to any shop.

As for code reader; you have 2 routes. I have icarsoft ($150-250) which is great as it reads all jaguar codes. Or you can get any cheap elm327 (under $25) bluetooth or wifi reader from Amazon or alliexpress. The cheaper option will only read obd2 codes and provide some engine pcm real time data. But it is better than nothing. If you want to keep this jag for a long time or you see a future jag in your garage; invest in the icarsoft reader.

 

pkoko,

Excellent advice on the icarsoft reader. This morning, I wanted to do a scan, so I got an inexpensive Innova unit that I could pick up today.

Also, a review of my service since April revealed that the fuel filter has, indeed, been changed recently.

Now, to the codes, which I think are indicating a catalytic converter replacement.

P0420-Low catalyst system efficiency
P0430-Catalytic converter not functioning efficiently
P0301-Cylinder 1 misfire detected (could be a coil, perhaps, but I think more likely a misfire caused by the faulty emission)
P1316-Random misfire
P2097-Post catalyst fuel system trim too rich in bank 1

I will use my scheduled regular service date on Wednesday to have this looked into, but I'm guessing it's something with the CC.

Thank you so much for your help and advice! Greatly appreciated!

 

This sounds to me like the car isn't getting good air (check the air filter filter, clean the MAF), buy a fuel system cleaner (the one I recommended, generic ones (STP etc) are mostly marketing BS), and hope the codes go away.

Otherwise, I have a feeling your O2 sensor on bank 1 is the main culprit. I know this is a hard job and the part is over $200. And I am not sure on our cars if we have 1 or 2 O2 sensors. Some cars have them pre-cats and after cats.

As for the mis-fire codes. I wouldn't worry about them unless they happen again on the same cylinder. Then a quick plug and coil inspection (with replacement if needed) maybe the course of action.

As regards to the coils, moving a faulty coil from one plug to another usually results in a missfire in a different cylinder. I will not buy a spare coil without this simple test first, unless it looks damaged.


Same strategy applied for injectors but I have never done such a job. So my info is amateurish at best.

 

Good points! All will be revealed on Wednesday, and I'll give the results when I get them!

 

@MyTexasJaguar, how many miles are on the vehicle?

Based on the DTCs stored, it appears there has been an issue with misfires for some time. One of the first things to do is find and correct the cause(s) of the misfires, which could be a vacuum leak, coil unit or the spark plug on cylinder 1.

The AJ-V8 cylinder numbering sequence is attached. Use the current ISO designation to locate each cylinder.

 

NBCat,

Thanks for your reply.

The car has 100,000 miles on it. When I purchased it, there were random misfires, so coils were replaced, and the misfiring issue was fixed.

I had a number of things replaced at the start. Along with a coilover, a new oil pan gasket, the coils, and after the coilover, a CC error appeared, but was cleared and didn't return.

Till yesterday. I'd planned the replacement anyway, and that's what part of my upcoming Wednesday service was to cover.

Thanks again!

 

OK, kids. One coil replaced. Running perfectly again.

Codes cleared on the catalytic converter issues. Going to wait to see how those go over till end of next week. If the code reappears, replacement.

Thank you so much for all your advice!