When I start my 2002 XK8 after setting awhile, maybe three days, I noticed it runs rough. And I smell unburned fuel. The exhaust note is also different. Sometimes the "check engine" lite comes on. But after it warms up and goes a few miles it smooth's out,and the check engine light goes off.
I recently bought a Autoengenuity scanner. It shows a lot more than my old one did. The error message said "misfire on #1,#2 and #3. It also said something about "emissions exceeded" .This would explain the check engine light. After it warms up the problem goes away.
My long term fuel trim is not right, it runs about 17.5 even when warm. The car has 90K on it, maybe I should change plugs as a matter of course. But I wonder what else I should look at. Any ideas?
If not for this forum I don't think I would have the courage to own this car. I belong to several other forums, and none compare.
Thanks to everyone.

 

Hi, Lanny. Just a thought here... I am thinking that your fuel pressure regulator may be leaking through the vacuum line, and the engine is stumbling while burning off the excess fuel during start up. It's easy enough to check. Locate the regulator on the fuel rail, and pull off the vacuum line (after the vehicle has set with the engine off) to see if there is a presence of raw fuel. If not, we need to be looking elsewhere.

 

You didn't say anthing about restricted performance but it could be coils ? If they are not firing right away it could be sending raw fuel and burning in the cats. Also check your plug holes, you could have O ring leaks and the plugs holes are filled with oil. just a few quick things to check. Cheers

 

The high fuel trim means the engine is adding a lot of fuel to compensate for a lean problem. Youcould have a vacuum leak in the intake between the MAF and the cylonder. Just start looking. If all is secure, report back.

 

I would not have thought about the fuel pressure regulator leaking. That would explain a lot. Thank you chopr.
I have tried to find an air leak to account for the high LTFT numbers. I used starting fluid, carefully applied with a "straw". This has always worked on my hot rods. So far nothing seems to show up. I was thinking maybe I should try to clean the MAF. I watched someone do that on Utube, on another type of car. When I pulled out the MAF on the Jag I did not recognize the construction. enough to take a chance. So I put it back in for the moment.

I will try again tomorrow. Thank again to everyone.

 

Watch the live short term data when using MAFS fluid or similar while directing it around the intake, egr valve, throttle body, hoses, connectors, etc.it spikes quickly without lways hearing the engine rpm varying.

 

Well, the first thing I checked this moring was the fuel pressure regulator as suggest by chopr. I was actually hoping to find some fuel in the vacuum line. But it was dry. So I am in the process of installing new spark plugs. I really don't expect this to correct the problem, but it is one more thing I can eliminate from my "do list". At 90K it won't hurt anything.
Speaking of hurt, the local NAPA store wants $14.50 each for replacement NGK plugs. So I looked at Amazon and they have them for about $7.50, except they say they will not fit my XK8!(??) So I went to the owners handbook to see what the factory recommends, and found nothing. I guess in the proper world of JAG you call "your man" to deliver the car to a proper garage and make it all well. After some searching I found a Boush plug that Amazon assured me would fit, price around $6.50. So, that is what will happen. I suspect I still have an unknown issue to solve. I think the high LTFT has to be a clue.

 

Probably too late.......JTIS sez NGK PFR5G-11E torqued 25-29Nm.

 

Spark Plug recommendations are buried in the Vehicle Care Handbook but detailed in JTIS. It's in Powertrain - Engine Ignition - Specification section:



Graham

 

Thank you GGG! I guess the plugs it had were the right ones for this car. The full # was
BKR5EIX-11. For some reason the Amazon website showed they were not right for this car. I hope the Bosch I ordered are correct.

 

Spark Plug codes are a minefield!

Here's an extract from the NGK Part Finder:



This shows the correct Spark Plug for your vehicle is PFR5G-13E. However this has been superseded by an upgrade:



The upgrade is BKR5EIX-11. This is the number Amazon had shown you was not right for your car. I can't find a direct Bosch equivalent for this plug.

Graham

 

I received my new plugs from Amazon yesterday at the end of the day. They are made by Boush. What I did not expect is that they are the type that has 4 electrodes instead of the one in the middle like normalplugs. The illustration shown in the Amazon picture was not like this.
I have a buddy who says he tried this style in his 280Z and they did not work very well. So I need to decide, do I give them a try,since I have them in hand, or send them back and order the right ones? The NGK plugs that Amazon says don't fit my XK8. Decisions,decisions.....

 

I think at least one of the members claimed that those plugs did not work well. If you do a search you should find lots of discussion. I am using the NGK BKR5EIX-11 that Graham pointed out and bought at one of the local suppliers at a good price.

 

I have been using Bosch in my xk8 & s-type for as many years as I owned both cars and they work just fine. The Bosch +4 is what you have and it is what I am using. You will be just fine!!!

 

I installed the Boush plugs today. It gave me a chance to look at each of the old plugs carefully too. They looked OK to my eye. Sort of white ash looking in the middle with a certain amount of soot on the edges. Pretty much what I would expect.
I will report back at some point as to how the 4 prong Boush plugs seem to be working. I really don't expect to see any difference.

 

The Boush plugs seem to be working fine. For some reason my LTFT dropped from 17.5 to around 12.5. And the STFT is hoovering around zero. I don't think the plugs would account for this. Maybe I fixed something by accident when I was replacing the plugs. I will take what I can get.....

 

It would do no harm to perform a hard reset
https://www.jaguarforums.com/forum/x...ect-faq-74146/
This will reset all your fuel trims so you can see if R + L banks stay good.