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[Gaffers]

Spent some time today diagnosing the misfire on kitty (XJR6 X300'97 - last of the real jag straight 6's) and amittedly the lack of spare time means that it has been a while since I last looked at it.  Because of this i started from scratch with the diagnostics.

In Park - misfire is present through out the rev range and the engine is lumpy on idle despite high revs
In Drive - misfire is all but gone, revs drop to normal

Regardless of gear the engine responds perfectly to the accelerator, can take a while to come back down.

At idle:
Pulling plug leads one by one I saw that cyl 2 was the one misfiring.
swapped dis pack with anoth cylinder = no change
swapped plugs = no change
removed ECU and traced wiring back = no wiring issue
removed MAF plug = no change in revs

The last work done was changing the ICV Stepper motor but I havet driven her since.

So, my thoughts are now either air leak, faulty MAF or Ineed new injectors 

[T.m.f]

Could try swapping injectors around 1st and see if it still miss fires on no2 cylinder

[aaronjb]

yeah I'd go with that plan. How did the plug look on that cylinder, any tell tales?

[Gaffers]

yeah I'd go with that plan. How did the plug look on that cylinder, any tell tales?

Sooty except for the end of the tip and the centre

[tunnie]

Does the cat run on gas?

[Andy H]

Spent some time today diagnosing the misfire on kitty (XJR6 X300'97 - last of the real jag straight 6's) and amittedly the lack of spare time means that it has been a while since I last looked at it.  Because of this i started from scratch with the diagnostics.

In Park - misfire is present through out the rev range and the engine is lumpy on idle despite high revs
In Drive - misfire is all but gone, revs drop to normal

Regardless of gear the engine responds perfectly to the accelerator, can take a while to come back down.

At idle:
Pulling plug leads one by one I saw that cyl 2 was the one misfiring.
swapped dis pack with anoth cylinder = no change
swapped plugs = no change
removed ECU and traced wiring back = no wiring issue
removed MAF plug = no change in revs

The last work done was changing the ICV Stepper motor but I havet driven her since.

So, my thoughts are now either air leak, faulty MAF or Ineed new injectors 

Those two symptoms shout air leak but I don't understand why the ECU doesn't control the idle speed correctly (unless it is a very big air leak)

Where does the brake servo vac pipe connect to the inlet manifold? is it straight into cylinder 2?

Is this a car that has worked for you in the past or is there a chance that a bodger has had a go at it before you?

[Gaffers]

Does the cat run on gas?

No i need to get her running well on petrol first

[Gaffers]

Spent some time today diagnosing the misfire on kitty (XJR6 X300'97 - last of the real jag straight 6's) and amittedly the lack of spare time means that it has been a while since I last looked at it.  Because of this i started from scratch with the diagnostics.

In Park - misfire is present through out the rev range and the engine is lumpy on idle despite high revs
In Drive - misfire is all but gone, revs drop to normal

Regardless of gear the engine responds perfectly to the accelerator, can take a while to come back down.

At idle:
Pulling plug leads one by one I saw that cyl 2 was the one misfiring.
swapped dis pack with anoth cylinder = no change
swapped plugs = no change
removed ECU and traced wiring back = no wiring issue
removed MAF plug = no change in revs

The last work done was changing the ICV Stepper motor but I havet driven her since.

So, my thoughts are now either air leak, faulty MAF or Ineed new injectors 

Those two symptoms shout air leak but I don't understand why the ECU doesn't control the idle speed correctly (unless it is a very big air leak)

Where does the brake servo vac pipe connect to the inlet manifold? is it straight into cylinder 2?

Is this a car that has worked for you in the past or is there a chance that a bodger has had a go at it before you?

Me too but i cannot find it.

i doubt it. To replace the ICV SM you have to take off the entire intake/iintercooler/tthrottle body.

I guess its my fault and i need to redo it

[Kevin Wood]

Sounds to me like it's only when very lightly loaded, so when injector duration is at a minimum. Might be a lazy injector that isn't opening under such conditions, or is dribbling away all the time, meaning the mixture in that cylinder is too rich. Once the duration is up and the engine is under load, the dribble becomes insignificant.

Worth checking the compressions just in case something else is up, but also try swapping the injector to another pot.

[Kevin Wood]

Just to add, you can send injectors away to have them cleaned, refurbed and tested.

I've used this place before with good results: http://www.injectorcleaning.co.uk/post.htm

A lot cheaper than a new set and they normally come back in perfect nick.

[aaronjb]

I was thinking the same Kevin and another vote here for www.injectorcleaning.co.uk, good service and the turnaround was only a few days from posting off to getting back.

[Gaffers]

Sound advice, and easier to do than stripping everything down again (you think that Omega inlets are fiddly?)

Injectors easy to remove, are they?

[henryd]

Surely a compression test is first point of call 

[tidla]

Surely a compression test is first point of call 

I was thinking the same thing. Then some mentioned LPG and i ran away.

[Andy H]

Spent some time today diagnosing the misfire on kitty (XJR6 X300'97 - last of the real jag straight 6's) and amittedly the lack of spare time means that it has been a while since I last looked at it.  Because of this i started from scratch with the diagnostics.

In Park - misfire is present through out the rev range and the engine is lumpy on idle despite high revs
In Drive - misfire is all but gone, revs drop to normal

Regardless of gear the engine responds perfectly to the accelerator, can take a while to come back down.

At idle:
Pulling plug leads one by one I saw that cyl 2 was the one misfiring.
swapped dis pack with anoth cylinder = no change
swapped plugs = no change
removed ECU and traced wiring back = no wiring issue
removed MAF plug = no change in revs

The last work done was changing the ICV Stepper motor but I havet driven her since.

So, my thoughts are now either air leak, faulty MAF or Ineed new injectors 

Those two symptoms shout air leak but I don't understand why the ECU doesn't control the idle speed correctly (unless it is a very big air leak)

Where does the brake servo vac pipe connect to the inlet manifold? is it straight into cylinder 2?

Is this a car that has worked for you in the past or is there a chance that a bodger has had a go at it before you?

Me too but i cannot find it.

i doubt it. To replace the ICV SM you have to take off the entire intake/iintercooler/tthrottle body.

I guess its my fault and i need to redo it

I think I am missing something here  was it OK before you took it apart?