Loss of Pressure in Bank of Cylinders V6 - Help!

I

ishnov

New member
Have a 2017 V6 R-Dynamic RWD low mileage (30,000) with zero mechanical issues until now.
Went in for its 60 Month / 80,000 mile service in April to a Jaguar Authorised Dealership passed MOT with no issues
Within 2-3 weeks car started misfiring with Engine Warning Sign coming on - returned to dealer
Dealer reported one of the spark plugs fitted during the service was faulty ('cracked') replaced it and that car was now running fine
Within 2 days recurrence of the misfiring and returned to dealer who then diagnosed 2 x faulty Catalytic Convertors quoting £4k job to replace
Cutting a long and frustrating story short I wasn't standing for what the dealer was telling me and had to convince them and Jaguar Head office that something else must have been causing the Cats to fail at this age of vehicles - took weeks to convince them of this !
Eventually got the original diagnostic codes as follows:

P0236-85 turbocharger/supercharger boost sensor A circuit range/performance- signal above allowable range.
P0420-00 Catalyst system efficiency below threshold bank 1 - no sub type information.
P0300-00 Random/multiple cylinder misfire detected - no sub information

Jaguar have been guiding the dealership on series of test with the problem remaining undiagnosed - next step is they are stripping down the cylinder head as they are now saying there is a loss of pressure across a whole bank of cylinders (not just one)!

I'm not a technician but have been taking some independent advise that this whole saga is really strange - convinced that something the dealership did when in service has created this

Attitude of main dealership whilst this has been going on is unbelievably bad and obstructive which make me even more suspicious of what has gone on. Trying to keep Jaguar UK Head Office onside in order to maximise chance of financial contribution to whatever mess I am left with despite it being out of manufacturer warranty

Would really appreciate guidance from those more educated than me on the subject and what levers I could pull for more support
 
First post of woe. Sorry to hear this and hope you get it sorted.

Have you had the car since new?

Ensure you have case open with customer experience centre.

CUSTOMER EXPERIENCE CENTRE
Phone Lines Open; Monday - Friday 09:00 - 15:30
Phone: 0345 303 2303

Abbey Road, Whitley
Coventry
CV3 4LF

Email Hours: Monday - Friday 08:00 - 16:30
Email: [email protected]
 
SimpleR
Thank you for your reply - yes had it since new and not a single problem until now !
I have got Jag Customer Experience involved and they originally agreed a financial contribution to the replacement Cats!
I had to convince them to support an investigation as to the root cause - could have ended up paying £4k and then finding the same thing happening !
 
What they are saying doesn't make sense .what does lack of pressure across a whole bank mean ?. You have 3 cylinders in a bank each has its own compression I would dowt you would suddenly lose compression in a whole bank. Its sounds to me like they cracked some spark plugs fitting them and they have caused a misfire which then causes un burnt fuel to damage the cats hence now needing new cats.
 
api330
That was exactly my thoughts that the faulty spark plugs or their fitting had caused the problem.
I believe Jaguar Head Office have been directing them to rule out all the likely issues of misfiring such as injectors and then I was told the fault was showing as low compression on one cylinder head which now needs inspecting.
I then asked if this was pointing to a broken piston, cylinder valve or gasket to which I was told
"it's a bank so I would look more towards head / block"
They (dealer and Jaguar Head Office) keep telling me that until they strip down the cylinder head they can't tell what has happened
 
Bit of a coincidence that a car that was running perfectly suddenly goes bad after a dealer service. Makes you wonder what they did to it.

Hope you can get it sorted out to your satisfaction.
 
scm - quite and I do hope there is a resolution without it costing me £'000s as it is not for the want of trying - on my part at least!
Have to say the attitude of the dealership has been appalling and makes me very suspicious of what they did during the service - fact is I have been with out my car for nearly 3 months and they just want it off their premises.
 
I agree with the general consensus of posts here
Highly unlikely that a perfect running engine co-incidentally starts to fall to pieces after a service
Dealer breaks plug or it otherwise fails
Consequential unburnt fuel damages cats.
Loss of pressure on 3 cylinders seems highly unlikely. There would have to be a gasket failure across 2 pairs of cylinders or a catastrophic head, rocker failure. Indicates something else related to plug happened to head or block. Possible warping, etc.
Dealer (mechanic or otherwise) is both concealing information or otherwise floundering around for a solution

I would advocate independent assessment to assess real issue. Ask the dealer not to touch the car and take advice, else risk obviscation of issue and a huge bill to foot.

Minimise posting on this thread as dealer and JLR read it.
 
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