I won't go into the full story here, I will post it later, but briefly, I have a 4.4 NA Jaguar AJ41 engine which was LPG converted (before we bought the car), and has recently started to misfire. Cam Tech Craig has confirmed that this is almost certainly due to valve seat regression

The acknowledged experts to get hardened valve seats fitted to my heads are JE Motorworks in Coventry, unfortunately they are working on a very big contract at the moment and will be unable to assist until next year!!

Does anyone know of a reliable workshop which could fit hardened valve seats? - I have read a lot of horror stories here and elsewhere regarding 'cowboy' engine building outfits.

Grateful for any advice anyone can offer as I really need to get the poor FF sorted sooner rather than later. 2006 (56 Reg) 4.4 V8 Vogue In Bonatti Grey (Gorgeous!!)

any lube system fitted?

how many miles since lpg system fitted?

have you had calibration of lpg system checked?

does it misfire on petrol?

all cylinders misfiring or just the same odd one/s ?

so many questions but may not be worse case scenario yet

No Lube system fitted (LPG system installed by previous owner - I questioned the lack of lube system 3 years ago when I first had the LPG system serviced (by the people who had originally fitted it) and was told it was not necessary as i didn't have the SC engine - as I now know, that was B**locks, I can only assume he was mistaking my AJ41 for a BMW M62, which of course has hardened valve seats and hence doesn't suffer from valve seat regression).

Don't know exact mileage since system fitted, but i have done just over 50K in the car since buying it.

LPG system regularly serviced by firm who originally fitted it

Misfires on petrol as well as Gas (Only been running on petrol for last couple of thousand miles to try and slow down worsening of the problem (which is gradual but is happening).

Cylinder 2 only misfiring

Has been checked out by Cam Tech Craig, who confirmed the Engine is running perfectly, therefore the issue is almost certainly valve seat regression. 2006 (56 Reg) 4.4 V8 Vogue In Bonatti Grey (Gorgeous!!)

get everything done on that number 2 misfire , new coilpack , new plugs , new lpg injector ,

before you leap into having the heads off ,

if valve seat recession it would be probably on more than one cylinder IMO , unless you've had a long standing issue on the gas injection into that cylinder running lean.

good luck

Already been done sir, there is less than a 0.0001% chance it is anything other than valve seat regression - incidentally, the guy at JE said in their experience valve seat regression on this type of engine has been found to occur anywhere between 40 and 70k miles - as stated above, I have done at least 50, and so am 'in the zone'

When looked at by Cam tech Craig at the end of last month, I was also getting an occasional 'misfire cylinder 7, fault. As we were unable to get anything sorted quickly, and my wife and I were due to take our 2 deer hounds (precluding hiring a car) on Holiday to Scotland at the start of this month, his advice was to run on petrol only as this may prevent matters getting any worse - I have had no cylinder 7 faults since, but cylinder 2 is very definitely misfiring, and it is neither the petrol injector, gas injector, or plug / coil pack etc.

There is no doubt that the one or both of the exhaust valve seats in cylinder 2 has regressed, the heads are going to have to be re-worked, it is just a case of who can do them, and make a good job of it. 2006 (56 Reg) 4.4 V8 Vogue In Bonatti Grey (Gorgeous!!)

Would a compression test help to show a valve problem on this cylinder compared to the others?

Although it that is the problem than I'd expect it to be effecting other cylinders also, if not now then certainly in the future.

Thanks for all the suggestions guys, but the diagnostics have been done and the fault has been confirmed(as far as is possible before stripping) to be valve seat regression. As I said in my original post, what I need is the details of a reputable workshop who can re-work my cylinder heads. 2006 (56 Reg) 4.4 V8 Vogue In Bonatti Grey (Gorgeous!!)

I'm not very familiar with your engine, but would you consider stripping the head and lapping the valves by hand to hopefully help the misfire till your garage could replace the seats?

you could try these in nwales

http://peterjonesengines.co.uk/engineering-services/

You could speak to Sturt and birch 4x4 in liverpool, I have used him a few times he's reasonable with price's

http://www.birchmotors4x4.co.uk/#home

the Jag engine is made of toffee, I personally wouldn't waste time on getting 1 side done, pay the extra get it all sorted, maybe even cost up a second hand engine ? LPG and jag engines is poor, I have a nissan murano which to is normally crap on LPG I fitted a lube system but it's never worked since i installed the system, I did however fit a fuel catalyst into the tank, this has put my mind at rest while running LPG and lube not working

even if you do fit a lube kit, I would always reccomended a fuel catalyst as well

http://www.ebay.co.uk/itm/350865504828