Kevy1, looking through your posts, I don't see a year or model of your car posted. That might be relevant to this thread, as there are alot of different issues with 4.0 vs. 4.2 vs N/A vs. supercharged. Coul you add it to your signature?

 

Hi Mike Thought id put that on my profile

Its an S type 4.0 X reg that's 2001 in UK only 64k with full history and all mot's to back it up, lovely piece of kit looks amazing just this anoying misfire

 

Any codes? Even pending codes?

Check battery volts after overnight stand without starting engine, should be at least 12.6V

Being a 4.0, has it got the revised metal-bodied tensioners (& associated parts)? (Hint: probably not, engine destruction awaits.)

 

My thoughts, too. If timing slipped, it would run rough all the time. I'd be looking at fuel trims and and codes. This is not rocket science as far as how things work......compression, fuel and spark as has been pointed out. Can you DIY this or do you have to rely on a garage? Do you live near Ed China? Put a fuel pressure gauge on it and make sure that's not an issue. An OBDII code reader might show some codes at the time that it's running rough. A few people have had to replace their ecu's; I would expect it would take a dealer's diagnostics to tell you that. Keep plugging away, the members here will help.

 

My garage had changed all plugs at £100 he said no codes what so ever! Checked fuel pressure no probs, checked for vacuum leaks nothing found, changed fuel filtet, fitted injector clesners, misfire comes and goes, took her back today in the hope the ecl light coming on just the once might throw a code? Nothing zippo he can't find a code to give him something to go on!!
He's a V8 specialist two Corvettes up on ramps in his garage, a 5.0 Porche outside! He didn't charge me for this 2nd diagnostic and apologied for not finding the fault am going to change all 8 coils next and add some cat cleaner.
The battery is a new Yausa 12v 100ah 900 amps £129 ,
Am booking in to a Jag specialist next month.
Perhaps I should have done this in the 1st place ; ( V8 specialists my @rse gave up on me!!

 

Ps Mike Ed China?

Thanks Guys, so many other threads on the net about these wonderful cars driving owners crazy with this Fking misfiring saga!!

 

About a month ago I was experiencing a misfiring with a sort of popping sound when I attempted to accelerate more quickly than usual. I took it to my mechanic to scope it and it threw a number of codes, but two stood out. One fuel injector was no good and a cam sensor was not functioning. Both were replaced although it took several days, but all is well again. We went ahead and replaced plugs since it had been a very long time.

Hope you find your problem soon.

 

A jag indy looks the best bet.

 

Another nasty secret i've found, ABOUT THE COILS,NEW OR USED.

Take the rubber boot off with your hand, you will see a spring held in place,a little flimsy spring, they are often burt brown and black,AND DON'T HAVE THE PROPER HEIGHT AND TENSION,(MEANING NOT TOUCHING THE TIP OF THE PLUG GOOD).

Simply scuff the little springs with a green pad for dishes, until they are shiny again, and then stretch them some so that they make nice contact with the spark plug tip.

When doing my valve cover gaskets, I had noticed the new valve covers are thicker-a redesign.This put some distance in between the coil springs and plugs, so I had to stretch the spring out , so they make good contact again,I was mis-firing after the job, so I know I did something wrong-hmm
NO CODES

New or old coils it don't matter, stretch those little springs.


Also, in your case, go to the parts store,get you some MAF cleaner,remove your air duct to spray down the inside spring looking thing of your mass air flow sensor,until its shiny new, then let dry.

Our jags coat them in oil, the sensor element bakes the oil onto it, reducing performance as well. NO CODES


3.Your mileage may have carbon coated pistons,get a good fuel injection service cleaning from a shop,as your knock sensors will hear that and retard timing , feels like a mis-fire, but is not.
NO CODES

4.This may sound stupid, but if you have VVT-Variable valve timing and have dirty oil, or the oil is thick, this will cause VVT timing issues, as their passages are very small and need a light clean engine oil.NO CODES

5.There is a plug near the throttle body, with a lot of pins,unplug it, clean with electrical cleaner, and make sure the pins have good contact with one another.Often I find those green tarnished, causes a host of mis-fire type issues, NO CODES.

6.You mechanic should of ohm'd all your injectors while the engine was hot,the injector that is different from the rest is the bad one, same for coil packs. CODE MAY COME UP MAY NOT


I investigate vehicles and design flaws, as I'm a mechanic.

When it comes to inspecting the works of a vehicle, let me tell you, Jaguar spends way more effort into "appearance", than "mechanical design",you should write their engineers.

Ive found most are just kids with computer drafting skills and have little physical or mental knowledge about heat dissipation in the engine bay,wiring gauge thickness for long stretches and high heat environments,or even ground noise isolation and emi protection,(not from outside sources,but the modules themselves causing this to other modules).

And no knowledge of accessibility of mechanical and electrical components to reduce labor hours, to save the company and you on repair cost. In my personal opinion, I would fire them.

 

Ditto ... although some on JF think they are some kind of infallible species.

On the accessibility thing, it often starts to make sense if you consider ease of robotic assembly.

For example, the hoses under the V8 intakes .. makes sense if you consider that they don't want pre-attached hoses flopping about during shipping and installation. I said makes sense as opposed to desirable.

 

Sorry to tell you, no robotic arms used for our jaguar for mechanicals.

Here is a jaguar robotic man pissed off at his job, though.

 

The good news is most (maybe all?) of the listed items are either fixed or at least do flag codes for later cars such as mine.

 

Kevy1 - I am with AODE06 on this one.

Misfire, no fault codes = coils. Replace all of them. If I have a misfire I do that before touching the plugs, works every time.

As usual there is agreat advice & experience in the posts. Check everything: for any splits or holes in hoses, chaffed or damaged wires. Even check the small wires around the coil connectors - unusual but it has been known for a damaged wire to cause a very hard to detect problem.

Sticking my neck out...you have nothing to worry about, it's the coils. If not I will apologise big time.

The V8 engine on the S is not the same as those of the XK so tensioner issues are rare if ever. Sometimes replacing a single or 2-3 coils does the trick until the remainder start to go - other times it causes(?) or maybe fails to fix a number of faulty ones. Under load and hot they tend to break down.

It is a DIY job, hardest bit is getting to the cover bolts. I use a very long flexible driver that happens to have the right hex socket on the end. I've just had to fix coils on my XK and that drove me so nuts after x4 I still could not hit the fault so did them all. There were no codes...just a grrr. misfire...now all is well.

Indie-wise worth talking to Kevin at DesignXKR in Andover: info@designxkr.co.uk

 

that's an expensive way to find you've got a problem with your plugs! Given my recent experience, I think it's worth checking the cheapest/easiest fixes first.

 

Thanks guys, Ive finally booked her in to Jagcare.co.uk
nr Portsmouth which is only 40 mins away from me, I'd thought about taking to tljaguar.co.uk
They do performance upgrades and all sorts of engine repairs, however its a long way from me and i got worried about labour charges.
Will let you all know how it goes ?? Fingers crossed they can nail it.
I've a niggling feeling it's arching coils!!

 

I did think about going for the change all coil option but as you say its an expensive way to go about it, to then find out its something completely different.

 

Hi,


I recently had some maintenance work done that made me think of this thread.


My 2000 XKR also had a misfire under heavy acceleration. I had all the basics checked out at the shop- fuel pressure checked, spark plugs changed, fuel filter changed, compression test on all 8 cylinders.


My fuel pressure was great. Compression was very good and within specifications. and upon having the spark plugs and the fuel filter changed my misfire is gone. Smooth, linear acceleration. I could almost notice the improvement immediately upon starting the car- and I never even thought it ran rough before.

 

I just went through this, total nightmare,your coils are 14 years old, and no longer working as intended under demand.

The average coil life is 60,000 miles, its considered a tuneup item to me.
You can try to remove the boots, clean the springs with a scuff pad and reassemble, to help some.

If your spark plug wells have oil in them, repair the valve cover gasket and grommets first,as the oil heats up, the condensation will misfire as well.

Also ohm check all injectors, replace the one that does not ohm the same as the others, and clean your throttle body.

 

Don't get it stuck in your head that it's necessarily coils.
I had misfires reported on two consistent cylinders.
One of the first things I changed was coils on a 75k car.
No difference. Changed the plugs around, no change.
Since I changed my MAF, I haven't had one code reported.

I know I still have a leak in both breathers, but the MAF change has sorted the misfires out.

I didn't expect that to be honest, since a faulty MAF should affect all cylinders. Perhaps the leak on one bank + the MAF was enough to cause a misfire, now the leak on it's own isn't.
Anyway, sure coils are a common source of trouble and you will have peace of mind once they're changed, but be prepared for no improvement!

 

My S type v8 is in with Jagcare in Portsmouth and they couldn't find any codes, all readings were good, they replaced some of the coils with some 2nd hand ones but made it worse so they are changing the whole lot, they reckon the original coils are all shot to bits and it's not worth changing one or two!

So obviously am praying that changing the whole lot will make it all good again??
otherwise as stated an expensive way to find out it something else
Will update soon


Cheers all