Not quite sure why everyone is stressing over the standard of the shop and what they did or did not do? I merely wanted to post my experience with the random misfire in the hope it may help someone else and what has solved it at least so far… particularly as I had not seen knock sensors mentioned in connection with a misfire. After all is done and with the claim on my extended warranty paid out it cost me 500 bucks to solve a random misfire. It’s so nice to drive without the misfire again! I will post a pic of the bill.This is a large indie JLR shop with probably 40 vehicles at a time, mostly LR but also Jags.

 

 

I don't think anyone is losing it. You mentioned they replaced a starter, but later clarified that you were demonstrating trust in the shop and it was unrelated. You stated 4 knock sensors initially. There are only 2, which you later acknowledged. You noted no code came - up but later indicated a code did show.

Not to offend, I think the way you phrased the thread, led some of us to believe you were possibly being bamboozled. Most guys here try to help ensure you get your car fixed and when relying on a shop, want to help keep each other from spending unnecessarily. Glad you got it sorted and looks like you'll have the short harness link you mentioned taken care of after the holidays.

 

Thanks Sean! Well said.
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So after the knock sensors were replaced there has been much improvement but the shop did say they still noticed a very slight misfire. They mentioned the engine harness link wiring was very fragile and so I have just had that job done. Someone mentioned previously they had been trying to track down a similar issue over several months and so I will report back as soon as I have road tested.

one thing I noticed after the knock sensors were replaced, exhaust tips are looking black now and poor mpg. Still no codes or cel. Will run my icarsoft again after I’ve done some miles…

 

Alan,

Thanks for the update. I was following with interest as my 2015 XKR convertible is nearing the 80k mile mark. What's your mileage? Other than "the sky is falling" low battery gremlins - E-Diff off & Dynamic suspension switched to bone-shaker mode - mine has been trouble free in my 1.5 years of ownership. I'd be curious to see what codes you get regarding your occasional misfire. In my German car experience, 100k miles = fuel pump(s) & coil packs, but I think that is nearly universal. My SOP for chasing misfires is to swap coil packs from the offending to the non-offending cylinder(s) and then see if the misfire moves - coil pack dying- or stays put - plug, injector, coil wiring, cylinder pressure, low fuel pump pressure causing lean mixture, coronal mass ejection hitting the point on the chip responsible for that cylinder's spark, etc...

I have yet to perform any extensive work on this beast and I find that once I do, I'll become more attached than any sane person should to an inanimate object. But I digress. That's just to say, I don't know of any reputational flaws inherent to this drivetrain, and your Indie Jag shop likely does.

Kidding aside, your symptoms, solution & side effects are very interesting. Was the knock sensor the problem or a symptom? If the ECU suspected a bad knock sensor, it would pull timing (and run pig rich) to protect the engine. But, the ECU would also pull timing if a good knock sensor perceived a problem. The black exhaust tips are a weird one, because that is a rich or unburnt mixture. Fuel trims would be another data point of interest.

I hope you found and resolved the underlying cause of your misfire(s), but I suspect you haven't. What does I-Carsoft tell you?

Regards,

Brian C.

 

After the knock sensors were replaced , yes 2 of 2, they still got these codes which led them to the wiring harness which was fragile and both codes were low circuit related. One is a knock sensor circuit and the other one is a O2 sensor circuit.
p0327 and p0137. However my icarsoft showed them as being “historic” so they may have already been fixed when they did the sensors who knows at this point!

They replaced the harness and say these codes are gone but still a slight misfire. It’s hard to find but they suspect a coil pack. Again no codes! I told them I’m sick of replacing parts but it was def better after the knock sensors were replaced. A coil pack would be covered by my aftermarket parts insurance. So will see…
93k km

 

This sounds like the start of injector failure - most things I've read show slow degradation and then a sudden failure of fuel dumping into a cylinder. Especially black tips and poor MPG. Definitely do cheap/free diagnostics first like swapping coil packs but you may be in for replacing a bank of injectors at least.

What's your fuel trims like and is there any cylinders missing more than others? Usually you can see a counter of misses (even if they don't trigger a code).

 

Thank you LJR today they say they they want to replace 4 injectors not sure if they are all on the same bank until I get to talk to them.

 

I would hope (for your pockets) that they're all on the same bank. If there were failing injectors on different banks I would just replace them all as it is a pain in the *** to get to. And if one has failed there's a good chance some others aren't far behind.

 

So this is the text string regarding injectors.what questions do I need to ask if any? If they identified which cylinder then why do I need 4 injectors, is that legit?
thanks all

 

I start my own thread as my 08 XKR had a rough idle and after warming up was fine I suspected a leaking fuel pressure damper. With great help from this form and a decent diagnostic tool and firing the parts cannon as someone put it at my car I have this down to cylinder 4 misfire, I notice if I rev it currently I can get odd misses on others. I have done the plugs all new with quad electrode racing plugs, coil packs, I will replace lamda and O2 sensors, I have them just not done it, but suspect injector on that one. The cost of injectors though is eye watering, I have had advice from independents and injector specialist that are not trying to sell injectors that you do not replace 1 injector.

The issue is if you replace 1 it will be off balance with the others especially due to the remaining having age, wear and tear and build up on them so you have a choice. replace all 8 or the other is to have all 8 removed and send them off to be sonically cleaned, tested and balanced. If you replace the one then later on you may have to replace another and another etc on the 4.2 SC its not going to be fund riping of the SC and manifolds every so often. So I am preparing myself for a big costly job but the outcome would be thousands of miles of driving afterwards. The cost of a clean, test and balance here is ?22 per injector, then you need the seal kits and clips at ?15 x8.

Thoughts/Opinions on this are welcome

 

It's like what Jaguar!2 is saying above, it's more cost effective and worthwhile to replace all 4 on a bank at a time since the amount of labour to do it is so high. If one is failing and they are all the same age/mileage, you're gambling on the rest if you only replace one.

 

Forum Tip: To get a member's attention in your post, "tag" them by putting an ampersand @ before their screen name. I just tagged you, @LJRXKR . You'll get an automatic email from the Forum that'll tell you that you've been tagged and a link. It's an easy way to keep someone in the loop.