Misfire on 1,3,5,7 Jaguar XJR S/C

[Lordgaz]

First post. Hi all
I have an ongoing saga with my XJR Jag 2004 supercharged. 118k miles. I have had all vacuum leaks fixed (there were leaks) on the car, fitted new MAP sensor (the one on the throttle body), had new spark plugs, and swapped over the coil packs from one side to the other, but I have a fault remaining which is a misfire all down the one bank, affecting Cylinders 1,3,5,7)
The garage also swapped over the existing lambda sensors to see if anthing changed but it did not

The garage is unsure where to go now -

Injectors? Cat? Camshaft Position Sensor (Could anyone point out where these are on the 4.2S/C - I guess there are 2, which could be swapped over)
Any experience of this type of fault ?

I have asked on a Jag forum, but I doubt this is car specific, so asking here to broaden field of expertise

Cheers
Gaz

[GreenV8S]

Is that the one with a charge cooler per bank? Check you haven't got anything blocking the matrix. I'd also compare the injector voltage and duty cycles bank to bank in case there is an electrical problem. Do they have a common fuel rail? Anything that could lead to a differential fuel pressure would throw the mixture out.

How bad is the misfire, does it vary with revs/load/temperature etc?

[stevieturbo]

How are you determining this misfire ?

Actual ? emissions ? fault codes ? other ? Can it report individual cylinders, or can it only report a bank ?

The fact it's on one bank ( or maybe one cylinder ? ), would point to a wiring issue more so than anything. If it was just one cylinder that might be different.

First basic steps, check codes, compression test, monitor emissions pre-cats on both banks and see how things are running.

[E-bmw]

stevieturbo said:

The fact it's on one bank ( or maybe one cylinder ? ), would point to a wiring issue more so than anything.

That is what would be driving me also.

[Lordgaz]

GreenV8S said:

Is that the one with a charge cooler per bank? Check you haven't got anything blocking the matrix. I'd also compare the injector voltage and duty cycles bank to bank in case there is an electrical problem. Do they have a common fuel rail? Anything that could lead to a differential fuel pressure would throw the mixture out.

How bad is the misfire, does it vary with revs/load/temperature etc?

Thank you for the reply, and sorry for the late response - (new members were restricted due to some forum abuse yesterday) -

Yes, 2 charge coolers (assuming you refer to the 2 silver boxes in the photo attached, and not something else) - We had stripped down as far as supercharger and throttle body removal and replaced seals and pipes to eliminate the vaccum leaks and rebuilt, but the issue was still there, so now stripping down again and looking at the injectors/fueling - There are 2 fuel rails - one for each bank - These will be checked - Hopefully the garage has the skills to do that. Although I am not yet sure at which point the codes for misfire are being thrown, I do know that the car would run ok with gradual throttle, but wide open throttle or high demand would result in a spluttering/ reluctance. So most noticable with revs

[Lordgaz]

stevieturbo said:

How are you determining this misfire ?

Actual ? emissions ? fault codes ? other ? Can it report individual cylinders, or can it only report a bank ?

The fact it's on one bank ( or maybe one cylinder ? ), would point to a wiring issue more so than anything. If it was just one cylinder that might be different.

First basic steps, check codes, compression test, monitor emissions pre-cats on both banks and see how things are running.

Thank you for the reply -
Code readout is below - It shows all of bank 1. Compression test passed ok -

[melhookv12]

I'd be checking the valve timing

[dingg]

Camshaft position sensor??

[Lordgaz]

melhookv12 said:

I'd be checking the valve timing

I've been trying to avoid thinking of an issue with valve timing, but it is a possibility - (reading about chains jumping a tooth due to broken tensioner etc) - Things get a lot more costly with this diagnosis - I will see if the garage is competent enough to check this - Though I would have thought that if this was the problem, it would present itself accross the rev range, and not closer to WOT - but can stand corrected.

[Lordgaz]

dingg said:

Camshaft position sensor??

Yes, this is on my list - No fault is showing for these sensors, but I have asked the garage to try swapping them over

[stevieturbo]

If there are no codes for a cam sensor, it is unlikely that is the problem.

And what were the results of the compression test ? On all cylinders ?

What are mixtures like on each bank when driving ok, and just prior to this issue ? The report mentions cat...presumably that is the same bank ? Have you got a visual on the cat in case it is blocked ?

Valve timing is possible....although if it was too far off I'd have thought the compression test might show discrepancy.

You could try swapping injectors bank to bank, but it's unlikely they are a problem. Also check ignition etc, wiring for coils.

[Lordgaz]

stevieturbo said:

If there are no codes for a cam sensor, it is unlikely that is the problem.

And what were the results of the compression test ? On all cylinders ?

What are mixtures like on each bank when driving ok, and just prior to this issue ? The report mentions cat...presumably that is the same bank ? Have you got a visual on the cat in case it is blocked ?

Valve timing is possible....although if it was too far off I'd have thought the compression test might show discrepancy.

You could try swapping injectors bank to bank, but it's unlikely they are a problem. Also check ignition etc, wiring for coils.

I'll try and get some data tomorrow.

[Lordgaz]

Lordgaz said:

I'll try and get some data tomorrow.

Could not get on the forum again (no newbie posts due to abuse again) -
All cylinders compression were in the range of 150psi so can eliminate cylinder wear, and valve timing I think?
The garage was going to start stripping down the engine again to check the injectors, but I have asked them to do a back pressure test on each exhaust pre-cat first to see if there is any restriction on the bank 1 exhaust due to cat obstruction (Due to the number of air leaks we had to fix, it is possible that the cat is already damaged from the lean running/misfires that may have caused))

[stevieturbo]

Sticking a small borescope camera into the exhaust to get a visual of each cat too is a cheap easy way to assess condition and possible blockage.

[Lordgaz]

Thanks for the input on this problem - It is now solved -

All the air leaks have been fixed, and supercharger bearings changed, along with valley pipe and other bits and bobs - For the misfires, I asked my garage to check the backpressure on the exhausts as I suspected CAT damage due to the previous air leaks - Found that both of them were blocked, (when we removed the lambda sensor to pressure test on one side, it was glowing cherry red inside) - Cats have been removed for now, and my god it goes like the clappers - Must have been like it for a while (or even since I bought it about a year ago)

[stevieturbo]

Good stuff

[Boosted LS1]

stevieturbo said:

Good stuff

Reminds me of a certain monaro with a glowing cat.

[stevieturbo]

Boosted LS1 said:

Reminds me of a certain monaro with a glowing cat.

Yea, but people in this thread listen lol