Good afternoon
I’m having problems with my 1996 Xk8
it has misfire on 4 cylinders
I have replaced the spark plugs,coil packs all 8,
checked the two boxes under the windscreen.
Just running out of ideas .
It rews up to 3000rpm and is cutting out
but when I reset the faults it’s running nice and smooth on all 8 cylinders till the rews drops down to 2500 and then the all faults coms back and 4 cylinders works.
Any help and ideas please

 

Is that one bank out, or two cylinders from each bank?

Note the engine is limited to ~3000 rpm unless the transmission is in a forward drive selection.

 

Welcome to the forums Arek,

I've removed the POLL from your post. It is not appropriate to the question.

Graham

 

What brand of coil packs did you use? Cheap aftermarket ones are infamous for causing more ignition problems than you were dealing with before....

 

+1 on NOT revving the engine unless it's under load as damage to the connecting rods can result.

Where is the vehicle located?

What is battery voltage across the terminals with the ignition OFF when measured with a voltmeter?

What is fuel pressure when misfires occur?

 

it is 2 on each bank

 

I have put Jaguar parts

 

When i had 4 misfires showing it ended up being my ECU. The capacitors are filled with saline and they end up leaking and corroding the traces inside. I sent mine to a place in texas, they went over it, repaired it, and no problems since.

 

early cars like yours have two ignition amp modules that run 1 bank each. also ECMs go bad as said above

if all good time to check check timing

 

+1 ECU. Two on each bank seems to be a common theme for the early model capacitors.

 

can you mention the place that did the work ?

Z

 

I had a similar problem on an XJ6, would rev to in my case I think 3,000 rpm (or maybe 2,000) fine but after that it went to pieces. It would no longer go above 3,000, misfires all over the place. Changing the crank position sensor fixed it.

Obviously different engine but a not dissimilar problem.

 

Hi,
The best way to check the ignition modules on the bulkhead/firewall is to swop the connectors between the two (the looms should be long enough), then check if the misfires change cylinders. If they don't, then suspect the ECM.

As noted by the others, the earliest ECMs are prone to failure. However, it's easy enough to remove and open up to inspect for signs of leakage.

Check these and report back.

 

It was done by "Foreign Auto Computer Repair" in Texas. Basically I searched on ebay for an ecu and it came up. I did some online review searches and they seemed ok. Some places charge almost $500 for the same service, but they are $250 including shipping back and forth.

 

ECU all day long! I had exactly the same issue on my October ‘96 XK8 last month. Misfire on the two outer cylinders on one bank and the two inners on the other. Checked and swapped coils and plugs - nah! That didn’t do it. Changed bulkhead mounted ignition modules - nope. Removed ECU, cut it open and immediately found a leaky capacitor. 20 minutes work with a soldering iron, reinstalled it and all is good now. Cost? Approximately 50 pence and an hour of work. As we say here in Lancashire (actually, I’m in the south of France currently), ‘Proper job’ 😀


Tin ECU in situ under the L/H bulkhead.

The offending article

The deposit on the printed circuit board.

New capacitor fitted and board cleaned with a cotton bud and some alcohol.

 

Gerard,
I would (and did) replace all of them, even if they're not showing signs of leakage. Where one has gone the others are likely to follow, and can badly damage the PCB if they're not caught in time.

See the pics in this post from greenforest56:
https://www.jaguarforums.com/forum/x...4/#post1779699

Did you drive down?

 

All good info. This is why this is the Best forum.

 

You're absolutely right Michael and I will replace the full set very soon. However, I needed to get the old girl running again for the Jaguar 100 event in Blackpool in September ASAP at which she's the 'star car ' for '96 (I think that's right as she was first registered on 1st Jan '97 but is an early build '96) and I've got very little time at home this summer having been in Belgium and Holland with work for the last part of July and then home for just 48 hours before motoring down to the Charente Maritime region on Friday/Saturday.
Sadly, didn't bring the Jag, largely because the fuel bill over several thousand miles would have been prohibitive, plus the memsahib's diesel BMW coupe/convertible with its 50+ mpg seemed to be ideal. So far, it's been great and I don't regret my decision, especially since I refreshed all of the rear control arms/bushes on the beemer a few weeks back.
Hope that you manage to make it to another show on mainland UK soon and that we can catch up again in person.
All the very best, Gerard