x308 mis fire engine mangement light on

[DREW]

took the leap from x300 to x308 Found a one owner 70,000 mile 3.2 sport x reg (year 2000)full service history, spent time looking/test drive all went more then well.Picked it up sat out on sunday engine management came on imagine my delight ! Car has been diagnosed as No.6 cylinder mis fire,car had a new ignition coil pack on that cylinder 5,000 miles in 2015.On another test carried out its not getting the full voltage to said cylinder. the mechanic has now said its best to take to a Jaguar dealer to be tested on there computer to trace the broken/damaged wire.Does this make sense ?As you can imagine not getting anywhere with the place i bought it from.
Thank you once again
Drew

[J44EAG]

Drew,

Was it a genuine OE Jaguar coil that was fitted?

Coil failure is usually caused by worn spark plugs. If your plugs are over due for a change, they may have such large gaps that the coil fails to be able to produce sufficient voltage to bridge the electrode gap. A worn plug can wreck a new coil very quickly. It is possible that the car did not have a plug change at the 60k service. I`ve had plugs mis-fire at 45k. A change sorted issues out.

I would start with new plugs and go from there. Ensure when you remove the coil, that the long well in the cylinder head is not full of water or oil. Ensure the coil and rubber boot are clean and dry. You might also check that the cap on the top of the plugs is tightened.

Using a code reader will help you further. The iCarsoft 930i at around £90, or a bluetooth ELM327 chip from ebay for a fiver used with a Torque Pro App and an Android or iPhone will give you a diagnostic solution. Remember diagnostic codes only point towards the issue area. After that you have to look at all components which are involved with the diagnosed area.

Mike K

[andypryce]

You could always get a 'cheapo' coil pack off eBay as a test to see if makes a difference, swap them round and if problem sorted there's your answer, OE coil packs are expensive, but I remember changing one on mine for a non OE one and it was fine, worth a try.

[DREW]

Thank you everyone. Car has been at garage Jaguar specialist for ages now.Latest is coil packs and spark plugs all swapped around still misfire at cylinder six.They reckon now it may be a valve problem or tappet problem but they cant be 100 % certain so iam left with "its going to be expensive to fix we have to take the head off to find the problem or put another engine in". All seems very vague to be left with a huge bill.I am at loss to think a 70,000 mile with full history can suffer such a problem in such a short time,all was fine on purchase 150 miles later and all this. I would very much appreciate some thoughts/suggestions
Regards
Drew

[J44EAG]

I wonder if the number six coil wiring needs a close inspection. I presume the garage are emphatic that there really is no issue with coils or plugs.

I would then be starting to look at a compression test followed by injector interogation if the compression test comes up as within sensible limits.

It is rather rare for a V8 with this mileage to suffer valve issues.

Have you ascertained that your engine number is a post Nicasil unit?

Mike K

[Orkney]

The code for coil 6 should be P1366. I had a similar problem with my SV8 shortly after doing the cam chain tensioners and I thought at first I must have disturbed the fairly fragile wiring to coil 7 (in my case) moved the coil to another cylinder and the fault code changed accordingly (on my highly recommended icarsoft reader which paid for itself on that fault alone). Bought 2 s/h genuine coils on fleabay for £12 delivered and fault disappeared. Would the CEL be illuminated with a poor valve/ low comp? If your fault stays on cylinder 6 I would be very carefully checking the wiring as Mike K suggests.
Ian

[ptjs1]

Coil wiring also for me! I'm assuming it's an intermittent rather than continuous misfire? In which case, it feels that a tappet or valve is an unlikely diagnosis. You could also check the injector spray pattern and possibly clear the codes and swap the injector with another one to see if the problem moves. Although I wouldn't expect anyone reputable not to have done this, did they also definitely thoroughly clean out and dry the spark plug well which can accumulate an extraordinary amount of oil which can then definitely cause a misfire.

After all that and with plugs and coils swapped, I'd remake the coil wiring to that cylinder. I certainly wouldn't let anyone take off the head or put in another engine yet!

Good luck

Paul

[J44EAG]

I fully agree with Paul.

One other thing comes to mind. That of oil sodden or rotten coil boots which sit between the coil and the spark plug. A long spring goes from the coil to the plug inside the boot. The insulation value or factor appears quite important and any breakdown in boot quality can cause the coil spark to run to ground. Putt-putt-putt.... Check that the spark plug caps are also tight to the plug centre electrode thread.

It is imperative to ensure that there is not oil or water present in the spark plug well. Water ingress can be caused by the cover seal leaking and also condensation. I drilled a run of 1/8" holes along the lower lid top edge to allow any condensation build up to vent to atmosphere on my old S-type V8. Dave Marks also recommends this small mod. Oil in the wells is the other issue and is usually caused by the cam lid "spectacle seals" leaking which fill the wells with oil.

You might also change the fuel filter which can easily become blocked and possibly cause the engine to run lean. Drain contents into a tray and look at the quality of the fuel. It can be quite diabolical and cause running issues. Filters are only a fiver or so and are well worth changing.

Mike K

[DREW]

thank very much gentleman I feel a lot more positive now reading your posts,I will read and digest properly and I am on the hunt for decent mechanic through my local region and will pass on your suggestions.
I will of course keep you all updated,once again thanks
Drew

[J44EAG]

One would hope that the 60K service included a full plug change. My 350R had a Main Dealer 60K service stamped in the book. In my opinion, the stamp should not have been applied unless the full service schedule and relivant parts changes had been carried out.

At 78K, I got a few misfires. Removing the plugs revealed huge electrode gaps and long term use stains on the plug insulator porcelains. Totaling the wear to the plug air gaps revealed nearly 6mm of air gap excess in total...No way had those plugs ever been changed even though the service book had been stamped. Thanks Mr Stratstone!

So the moral of the story must be that with an unknown new car, one really does need to remove plugs and see for oneself what the engine is still running on. In my opinion, service books and stamps only really indicate an attendance at a service bay and perhaps an odd oil change now and again. Am I cynical? Yes, indeed. I`m more convinced though about the size and content of any invoice pile which might come with a car. At least then one can pore through the invoices and idemise what parts may have been fitted dueing previous years on the road. Caveat emptor applies.

Mike K

[RichardSEL]

Good point on main dealer service (Service? What service?) And doesn't apply to Jaguar main agents alone.

Bought a "VW Warrantied" Passat from huge main dealer that shall be nameless in Swansea called Sinclair.
Good deal since I P/x-ed a manual Passat year older also from a local main dealer. So the inter-VW main dealer arrangements appled.
Subject to having all warranty services done by main dealer. That rule's now been outlawed as an artificial barrier to trade by the EU competition commission. But I digress... £290 inc for the third year final service and stamp in the book.

What did I get? An oil change. Done by suction pump thru the dipstick hole. And not even a filter change as I found out at my VW indi the following year. In the US there's an outfit called Bentley Publishers that publishes all the service schedules with what you should get done. And with handy charts to tick off. Plugs should've been done then and lots of other minor stuff.

Point also being: years ago service books used to list what you'd get done for each on a seperate page with a check box for the mechanic. Nowadays?

[Brakebuster]

from memory , the plug change on an X308 is 90k miles , so it would not have been done,

it really is an important issue to understand what you get for your ' service ' , ask for them to describe what you get before booking, preferably with a printed service schedule, and I always ask for the replaced parts to be held back for my inspection before they throw them , if they throw them before you inspect them then you have good grounds for refusal of payment, however, until you get the keys in your hand they can hold your car to ransom until you pay the bill , then it all gets messy , lol

for those that cant do this work yourselves and save many hundreds of pounds and actually know the work has been done, then its a bit of a mine field

BB

[RichardSEL]

Not £290, but £219 inc. Still a bunch of rip-off merchants though. But I'm over it now...

... " the technician that attended to you today was Robin b'Astard"

[DREW]

Next instalment -Bought car back the 25 miles home went like a dream. Engine management light on and still misfire just a few hundred pound down. Had the car plugged into RAC computer and read misfire cylinder 8 & 6 and malfunction of crank shaft sensor (never seen that before) so going to have that replaced.All good fun,till the next instalment
Thanks
Drew

[ptjs1]

Drew,

I'd be talking to one of the club's paid technical advisers before I started buying any new parts. Especially if there's a potential concern as to wiring integrity.. Getting a read of the fault codes is one thing but you can't conclude that the indicated parts are at fault necessarily.

It's worth doing more diagnosis with input from the right technical advisers before spending money.

Good luck

Paul