Misfire?

[dazav8]

Hello all, Got a quick question im hoping someone with some knowledge can help me on, Travelling on a main road the car starts to judder and RPM go right down and struggle to get past 50mph, Whilst this is happening the amber engine light flashes, I tried the odb scanner and it found 0 codes, I been reading around and sounds like it could be misfiring, My question is how do i check what cylinder is misfiring?

 

Thanks

[Russ68]

Hmmm, sounds like an extreme version of what I had when I bought mine, which was resolved with a full service including plugs and coil packs. If you haven't done them, there's a chance the ones under the inlet manifold haven't been done for years / ever! Manifold has to come off but well worth it. I went for a decent quality service kit from Berkshire Jag Spares and she's run like a dream ever since 

[Lazlo Woodbine]

I had a misfire on my V6 due to water splashing up from a puddle, running down into the spark plug well and shorting out the HT to earth.

Anyway, if it will misfire at idle then you should be able to hear which bank it's on from the twin exhausts. You can then unplug each coil pack LT plug in turn (this is safe to do while the engine's running). When you unplug one and it has no effect on it running, that is it doesn't get worse, there's your misfiring cylinder.

[dazav8]

Thanks for your help both. Ill try unplugging one by one and see what happens

 

[dazav8]

On 11/07/2017 at 11:22 AM, Lazlo Woodbine said:

I had a misfire on my V6 due to water splashing up from a puddle, running down into the spark plug well and shorting out the HT to earth.

Anyway, if it will misfire at idle then you should be able to hear which bank it's on from the twin exhausts. You can then unplug each coil pack LT plug in turn (this is safe to do while the engine's running). When you unplug one and it has no effect on it running, that is it doesn't get worse, there's your misfiring cylinder.

Well , Spent this morning testing 1 by 1 , Now either im doing it wrong or theres no problems with coils, Next is to change all the sparks, If the problem is still there i will look for vac leaks.

[Lazlo Woodbine]

Hmm. So unplugging any coil has the same effect? How bad is the misfire at  idle? Does it miss worse under load?

[JOE-DOT-COM]

Hi

If the EML light is on or flashing there should be a code

Is there any other code reader you can try on it, it would save a lot of time

cheers

Joe

[dazav8]

HI, Unplugging each coil one by one gives the same effect (slight engine noise change), It backfires when the engine has warmed up, It happens when idle too, But the car is perfect from a cold start until it warms up then it feels very sluggish then i get the flashing amber light, I have tried 2 code readers, the first one didnt work as it would not connect to the car so i purchased another one and it worked but showed no codes, I need a reader that can display pending codes i think.

[dazav8]

Im actually close to getting rid of the car as i have had so many problems with it, Its becoming a money eater, If i can get this misfire sorted it may be saved

[Lazlo Woodbine]

I have to admit I've not had a car with coil-on-plug ignition before this Jaguar and never had one fail so I don't know how they "go". But on a car with traditional distributor or single coil pack a misfire when warm but not cold makes HT leakage the number one suspect in my book.

Electrical insulation can break down when warm and allow the HT voltage to go to earth and not the plug(s). Usually not only will the running get progressively worse as the ignition components warm up but over a period of time as the insulation degrades further it can start happening sooner and sooner from cold . I can only imagine that coil-on-plug coils can fail in a similar way, as I say I've not seen a failed one, but the theory is the same.

It's easy for a fault to make a car seem like too much hassle to carry on with, but if you can then stick with it a bit longer because I have a hunch it's not anything too bad. Ask Joe and others about good code readers, there are lots of options. I've got a cheap and fairly rubbish one and wish I'd known more about them and spent a bit more..

There are other options for testing if you have a multimeter, oscilloscope and a healthy respect for high voltages. Otherwise a scanner is probably your best bet.

[Claws]

Hi Daryl

I had a little look around for you, I don't want to send you on a wild goose chase, but this may be a possibility? http://www.jagrepair.com/VacuumLeakSType2000.htm

Regards

Steve

[Russ68]

Mine only broke down under load, i.e. it idled and ran fine until you floored it, when it lost 1 or 2 cylinders. This would not have showed up when not under load, so I Laz's test would not have worked with mine. Getting rid of the car because it has a faulty spark plug / coil pack is a bit defeatist IMO, these are consumable items that should be replaced if you don't have firm evidence of them being done recently...

[Gary pile]

Had my car diagnosed misfiring on all cylinders as anyone had the same problem and how was it  fixed

[Wrinkly]

13 hours ago, Gary pile said:

Had my car diagnosed misfiring on all cylinders as anyone had the same problem and how was it  fixed

"Bite the bullet" and replace plugs and ignition coils. As you will need the inlet manifold off, you will need new manifold gasket/s as well. Had one cylinder on bank 1 misfiring and left it whilst I tried to find other reasons and it killed the Catalytic Converter. I eventually replaced all six plugs, coil packs and manifolds. Problem cured. Then had to replace the cat as that kept showing a code P0420 (Low efficiency left bank). Dear job but well worth it as the car has been wonderfully smooth and powerful ever since.

There are numerous posts which I put on this Forum about what I did and went through to cure my S-Type of this problem

Good Luck with sorting your car, Regards, John