My 08 2.5 has performed perfect in the 7 yrs I have owned it, and I have serviced more often than JLR specify.
plugs were changed about 3 months ago.
I f I drive it sedately it purrs along and changes up and down as normal, however if I give it some beans on an incline it seems to have developed a ‘Super Sports mode’ it changes down a bit too readily often as low as 2nd and happily sits in 3rd up around 40000 revs with no thought of changing up even if I lift right off the throttle when normally it would be in 5th. If I keep my foot down when its in 3 rd on a gradient then the engine light starts to flash and then it completely cuts out and in again rapidly, sometimes I feel like its just going to coast to a stop. Once on the level it gets its act together and the light will go out. It has stayed on sometimes and when I have gone in with my Icarsoft it says random misfire on cylinder 2,4,6. I have driven home with the data stream page on the Icarsoft to check things like fuel pressure, map sensor, throttle position etc, everything seems to show normal. The long term B1&2 fuel trims read about .500 to .700 and the short term B1 . 008 and B2 minus . 002 on constant throttle.
What is strange is its only plugs 2,4,6 that get flagged but the engine completely cuts in and out under hard acceleration.
The engine light has been coming on under normal driving the past few weeks saying Bank 2 catalyser below normal efficiency, I clear it and it goes several days before lighting up again, the lower O2 sensor was changed about 6 months ago with a Denso sensor. I don’t think its an air leak as it didn’t light up on over run when you have high vacuum, just constant throttle and now its really started misbehaving, any suggestions appreciated.

 

Find and correct the misfire(s) and DO NOT operate the vehicle under conditions that cause the MIL to flash as catalyst damage is occurring. If DTCs P0420 and or P0430 are present, catalyst damage has likely occurred.

Check fuel pressure and STFTs and LTFTs using the Torque app via a smart phone connected to the vehicle through the OBD port using a Bluetooth interface. List your readings here.

 

Norcat, well, you are lucky in that you got problems on the easy side of the engine. I would start with pulling the coil on cylinder #2 and seeing if you have either water or oil in the plug well. You have fluid in there, this can lead to misfires and the engine doing funny things. Next, I would look a little further to your left (when looking into the engine bay) and follow the ground wire of the coils to the ground connection above the tire on that side of the car. Clean those connections really good. You could have corrosion on these leads and it only acts up when the RPMs get up there. Having 3 of 6 cylinders all essentially drop out at the same will make the engine feel like it lost all power (in a way, it has). So, this is more a symptom of the 3 cylinders misfiring. This would also result in the catalyst inefficiency code(s). The part that I am trying to wrap my head around is why the tranny is holding the gear. All I can figure out is the misfiring cylinders is affecting the vacuum in the intake, which is affecting the tranny through looking at the parameters.

 

Thanks for the replies, tomorrow I am going to replace the plugs and coils as stated on the ‘easy’ side thank goodness. Today I drove it in manual mode and selected the gears when going uphill, if I kept it in 3 rd it got up the hill fine, only once did the light start flashing and as I hit 3000 revs the engine did its cutting out thing when it dropped below 3k it ran normal so I guess it was the power reduction kicking in. I think you may be onto something Thermo regarding the vacuum, I am not sure how the kickdown works on this box as its a few years since I used to rebuild Borg Warners gearboxes which were cable kickdown and a few were vacuum. I will report back on what happens.

 

Norcat, I think we need to clarify something so we are not chasing a problem that is not there. If your car is in limp mode (should say it on the information screen), if you raise the engine RPMs up above 3,000 RPM, then yes, the engine will cut out and reduce the RPMs back below 3,000. This is the car acting normal. The question then becomes, what is causing the motor to be in limp mode. I would be looking at the error codes and seeing what else you have listed in the error codes. It seems like you are missing something. This is where you could possibly have a vacuum leak, putting the car into the limp mode. Granted, I don't think this would explain the "super sport mode" that you talk about. I am thinking you may have a low fluid level in the tranny causing that,especially if you can manually shift the J'gate and things operate normally.

 

I think the fluid level is ok as I have changed the fluid twice in the 7 yrs I have owned the car and its bone dry underneath so no leaks.
The power reduction happened when I was going uphill in 3rd and the engine light started flashing indicating a misfire just before 3000 revs and as the revs went past 3000 it hit power reduction and as I eased off the revs it ran normal again. Its the first time I have experienced power reduction on a Jag and its like turning the key on and off, its quite violent! I am very familiar with power reduction on Volvo, Mercruiser, and most makes of outboard and they just smoothly ease back the revs, so Jaguars version took me by suprise making me think it was a seperate fuel related problem. I know what triggers the flashing engine light after experimenting, its only under load uphill, on the flat it just accelerates normally. So I now know its likely a coil/plug fault when the engine is working hard, it was the violent shuddering that threw me off track making me wonder about the fuel pump or worse.
when the misfire is fixed I will do an autobox relearn, I think the box is just sulking because of the erratic engine performance.

 

When mine went into "limp mode" climbing one of our ubiquitous Rocky Mountain passes, it was indeed "violent". Felt like turning the ignition key on and off on an old manual transmission car faster than a human could manually do it. Staccato style.

Does your icarsoft show any other codes besides cylinder misfires? And as NBCat mentioned driving can cause damage EXTREMELY quickly if there are certain other codes.

 

That describes it exactly, just like turning the key off. The codes I have pulled are random misfire on 2,4,6 and cat efficiency below normal. So looking back I think I have had a plug or coil playing up occasionally and now its really giving up, I will ve replacing plugs and coils on 2,4,6 as I have some spares and hopefully it will be cured.
My Icarsoft which is programmed for Jaguar for some reason won’t link up, probably needs an update. So I am only getting generic codes which don’t identify things in detail.
If I erase the codes the engine light stays off unless I work it hard uphill so am driving like a pensioner until I am back at work so I can fix it in the workshop.
I see you are in Utah, I have had some great ski trips up at Snowbird and Alta, and have driven out to Moab and the Delicate Arch several times, amazing scenery.

 

Further to my previous post about a Scitzophrenic Jaguar, I have replaced the plugs and coils on bank 2 cylinders 2,4,6 with some spare ones I had. I still get a flashing engine light when accelerating uphill, not when on the flat. If it flashes I immediately ease off the gas and it goes out, but if it happens a couple of times it stays on, and my Icarsoft continually says Bank 2 random misfire even though all the ignition components have been replaced on that bank.
My question is has anyone else experienced a misfire only under load having replaced the ignition components. It should rule out air leaks as the engine vacuum is low with an open throttle, it could be an injector but the car starts, idles and runs fine as long as you don’t push it hard.
I am wondering if my Icarsoft has me chasing the wrong bank, I am going to put brand new plugs and coils on the rear bank and replace all the upper and lower O rings so it should eliminate any problems on the difficult side, and run some injector cleaner through it.
It definitely sounds a bit offbeat when going uphill and it doesn’t pull like it used to and you can occasionally feel it missing when cruising but the engine light doesn’t come on, only when pushing hard uphill so it points to an ignition failure in my experience, but I welcome any solutions.
Its weird I spend my week diagnosing and fixing faults on marine petrol and diesel engines and big outboards, but when it comes to your own car you tend to get a bit blind and overthink things as you don’t want to mistakenly spend money on parts you don’t need. Especially as I live in Norway and everything is Expensive, like £20 for one spark plug! So I have to order from the UK.

 

I wish you'd stick to your other thread! https://www.jaguarforums.com/forum/x...jaguar-249369/

 

Thoughts:
1. you've swapped bad parts in
2. you've done the wrong bank
3. you have wiring/connector fault(s)
4. you have a failed cat. conv.

 

I had misfires on different cylinders for months, finally tracked down to intermittent fuel pump. JagV8 pointed out the repair manual specifically says misfires on random cylinders can be reported when the fuel pressure is too high or too low. I checked fuel pressure a couple of times with the OBD reader and Torque app. These spot checks or snapshots were always good. If I had been logging the fuel pressure I would have spotted the trouble with the fuel pump. Don't know if the iCarsoft will log data but it is a handy function, you can concentrate on the driving and not be staring at the live data on the little screen.

 

Read the entire thread but note post #8

https://www.jaguarforums.com/forum/x...-today-205696/

 

Many thanks for the info I will data log my fuel pump pressure on the Icarsoft and see what happens, it has been stable but will check it under load. Great to know you can cut through the floor as I have AWD so its a lot of work to drop the tank. I have used this method before on 2 of my Saabs so have the nibbler tool.

 

I've merged your original Help, Schitzophrenic Jaguar! and this Misfire under hard acceleration threads. The fastest way to annoy the knowledgeable and experinced forum membership is starting a new thread on the same topic.

I've also deleted your ADVERTISEMENT for X type 2.5 Cam covers. The only place for advertising on the forums is in MARKETPLACE. If you READ THE RULES you will see advertising in the Model forums results in a 7 Day Ban in the first instance. A lucky escape as I haven't imposed it.

Graham

 

Ok, thanks Graham.

 

I have checked the fuel pressure and its in spec all through the misfiring so I think I can discount the pump. I have ordered a full gasket set, plugs and coils from the UK and will report later when the parts are replaced.

 

Well finally got the parts from the UK so today did the following, new original Jag plugs, new coils, all new seals under lower manifold and upper manifold, also throttle body and inlet actuators, also checked the earth on each coil plug back to battery negative. So I think we can safely rule out ignitionproblems and airleaks. It started up fine and drove 20 miles without the CEL staying on as before so the cat is ok. It still flashes when going uphill, but stops as soon as you lift off the throttle or manually change down to take the load off the engine and cruises fine, after about 20 miles the CEL stayed on so I am back to square one and £200 poorer!
It has to be a fueling problem, I drove with my Icarsoft connected and recorded fuel trims as follows,
Idle. 1500. 2500
Bank 1 S 2 2 3
Bank 1 L. 3. 3. 5
Bank 2. S. -4. -2. -10
Bank 2. L. 0. 0. 0
These are average figures the Bank2 shortterm went as high as -17, and B2 Long went into low + figures on over run.
So it appears to be pulling back the fuel on back bank 2 and causing a leanburn misfire, but why is it reducing fuel, could it be a leaking injector which it is trying to compensate for, the plugs were all normal colour, or a faulty O2 sensor, the lower sensor on bank 2 was new
1 yr ago and its never thrown any codes for O2 sensors. My code reader was saying misfire on 2,4,6 but now after the work it just says random misfire.
I hate these kind of problems as I don’t just want to throw parts/money at it and hope I get lucky. What do the Jag experts suggest I try next?