Changed air and fuel filters last weekend. Car was recent purchase and performed fine when I bought it, but it had begun to be sluggish, particularly when pulling away from standing start, kind of like I was pulling away in second. Air filters were not too bad, but fuel filter was. I could barely blow through it.
Took it out today for first time since replacing filters. Still sluggish on pull away. Drove about 3 miles and car began to jerk and engine finally died. It smelt hot although temp gauge and oil pressure fine. Sat for a few minutes, restarted. Revved engine, let tick over, fine for about one minute then died again. Had it flat bedded home. Left it for 3 hours, turned key, fired up, ticked over smooth, revs up, but I don't think as quick as it should.
Anyway, while ticking over, placed my hand behind exhaust pipes. Drivers side was hot exhaust gas, passenger side not hot at all.
Now I am confused, if one bank not firing, why does engine tick over ok. ie, no bouncing engine, it sounds smooth, looks smooth.
Anybody help please.

 

The Jag V12 is more like two straight sixes rather than a V12. On earlier models with Marelli ignition it's common to have a dead bank and the driver not even realize it....except for the low power.

I'm not familiar with the DIS ignition system on your model so I'm not sure if losing one entire bank via ignition failure is likely or possible.

Anyhow......

Have you thought about a plugged exhaust? I *think* your model has a true, segregated dual exhaust system


Others will chime in

Cheers
DD

 

Hi Doug, honestly I do not know what ignition system is on this car. It seems from the state of the fuel filter that the previous owner did not do regular maintenance.
I have been searching the web since posting, and found a couple of other posts which suggested that a blocked cat converter could produce sufficient back pressure to prevent one bank from firing. Yes each side has its own distinct exhaust system, just like two sixes side by side.
I'm thinking and tell me if I am wrong, first step would be perhaps to check for current to the plugs on that cold bank, since your comment about owners losing the entire bank and not knowing it. Beginning to wonder, car has done 132,000, not a lot for 20 years, but wondering if the spark plugs have ever been changed.
I have a suspicion that the last owner ditched the car for a transmission issue. I say this because the transmission casing is so clean, and brand new looking I could eat my dinner off it. It reminds me of how my F150 transmission looked when it came back from the shop after a transmission rebuild.
If I have a spark at the plugs out of the engine, and of course gas to that banks injectors, then I am thinking maybe a blocked cat converter. It would explain the hot smell, and the car jerking I guess as the back pressure built up.
I'm kind of old school mechanic, give me gas, compression and a spark at the right moment and I'm good to go.
I very much appreciate your input Doug.
Richard in way to hot for November, Central Florida.

 

"Distributorless Ignition System"


Ignition Coil and Power Module-6.0 Litre - Parts For XJ Series from (V)720125 to (V)812255 (X300) | Jaguar Heritage Parts UK


I'm not sure of the typical failure modes. The system was only used for a couple years on a few thousand V12s....so there just hasn't been much discussion. But, someone out there will know more than I on the subject





Can't hurt; seems as good a place to start as any.

Cheers
DD

 

If it indeed is misfiring on one bank, shut it down and start reading.

There have been some spectacular fires caused by this exact reason
resulting in total losses.

 

Thanks Plum, you just managed to put fear of God in me. I assume then my first act is to check for spark on that bank. I assume the fires have been caused by gas still pumping into the cylinders.
I was amazed that a whole bank could be bad and engine still ticked over normally. If I lose one plug on my V8 GM truck I can feel the misfire.
I will check for spark tomorrow, and update result here, then maybe you could point me to where I should begin reading. I would certainly not wish to see the car catch fire.

 

Update. Both banks are firing fine. So discount coil pack and plugs.
Today managed to run long enough to get engine up to working temp and hot exhaust gases emitting well from both tail pipes.
At 1500 to 2000 rpm the engine splutters and almost stalls out, revs drop to about 1000 then picks up again. Both banks are affected by the almost stall, and the exhaust gases on both pipes hesitate. Some times the engine will recover and rev again, sometimes it dies. Opened air filter boxes to allow engine to breathe without filters, same symptoms.
My next move is back to basics.
I am reminded of a similar problem on my F150, whereby all of a sudden the truck would begin to jerk, semi or fully stall out, then fire up again in a minute or so. On that vehicle, the insides of the fuel filter had broken free, and were being sucked and pushed forward inside the fuel filter housing sufficient to almost or even fully prevent fuel from reaching the engine. New fuel filter, problem solved.
The problem I have now on the Jaguar has only appeared since I replaced the fuel filter, maybe coincidence, maybe not. However I think for the price of another filter and half hour of time, it has to be my next move to replace the filter again. If nothing else it will remove one more potential reason for the problem, and clear that one from my mind.
I will get to do this tomorrow or Monday and update again.
In the meantime if anyone has other ideas, I am listening.
Hope you are all having a great weekend.
Richard

 

Sunday. Changed fuel filter again and took opportunity to pump a good pint of gas out of tank looking for water. None present.
Had engine tick over for about an hour, LOVELY, but still wants to stall out at about 2000 rpm.
My thoughts, and actions. Disconnected MAP sensor on drivers side, engine clearly faltered and didn't like it. Reconnected.
Disconnected MAP sensor on passenger side, MADE NO DIFFERENCE. engine kept idling like I had done nothing. WEIRD.
My thoughts, change MAP sensor on passenger bank and see what happens. and perhaps look at Oxygen sensor on that banks exhaust pipe.
Any thoughts??????????
Richard

 

Update. Borrrowed MAP sensor from 96 model, made no difference. Back to basics. If it was my GMC or Ford truck, my thoughts would be bad ignition module or coil. So let me not over think this cos it is a Jag.
Like all sensible Englishman, I learnt before I left England for the colonies, just joking guys, that if you own one Jag, you better have 2, cos one will be in the shop.
So let the basics of my too many years of fixing cars and trucks guide me.
Change the coils. Yep bite the bullet and change the coils.Ok I will. Ok I did.
Did it work?????? Sure seems like it did, no stalling, no eratic rpm. Well spent $160 and half hours work.
DD and Plums, should you happen to read this, thanks for your input. If you haven't done so, check out my post about my 96 model ignition problem.
Richard