I was browsing the ads today looking for another motor and I came down to the last line and it says..... "Misfire upon heavy acceleration." I have not seen the car in the flesh so to speak and that line is the only clue I have. Its a 2003 XK8. Any obvious ideas as to what is wrong and probable fixing costs?

 

Bad coils, bad MAF, blocked cat(s), and any of a few others. Probably has codes worth reading.

 

Thanks. More or less what I was thinking. Trouble is the car is near my old stomping ground of Preston in a car show room and I am I Malvern in Worcestershire so code readings are not exactly practical. A 6 hour round trip to plug my machine in?

Blocked cat and coils sounds expensive. If it were a friends car I could fix it. A good cat cleaner, new coils, electrical spray cleaner on the MAF sensor etc. Will keep looking.........

Oh yes the car has done 154741 miles not exactly low mileage for a 2003 but known higher. Looks like things are starting to wear out.

 

The traditional first thing to check for hard acceleration misfires is bad spark plugs. The next thing is to check fuel pressure, the pump could be weak. Bad sensors will affect the entire rpm range, not just hard acceleration.

 

I am going to give this one a miss. Too many variations for solutions.

Thanks for all the replies guys. No need to suggest any more........

 

will my decarbonisation on Monday do a 'cat' clean too?
This misfire sounds like a restricted performance issue too - as the restriction would seem like misfire under heavy acceleration?

 

I have used CAT cleaners in the past and they seem to work. However after doing some research it turns out if you put the more expensive petrol in, gas to you guys in the USA, with the higher octane rating that works just as well.

Whenever I do upgrade to a XK8/R I will have it Terraclean'd. That should sort out a lot of problems. Just google it. I think I have the right spelling. Terraclean.

 

 

Hi all seems I have bought a V8 with either a misfire or judder, could be a fuel starvation issue?in general it drives fine but this is an annoyance that Id like to have fixed so its running as it should. I traded it for a lovely 3.0L manual in almost perfect condition so am a little gutted.
Basicly it feels the same as sticking points on the older style cars at idle the engine almost cuts out,fine when revs are higher, I've put it in to have a diagnostic done but no fault codes have been found????

They've changed fuel filter and now changed all the plugs and checked the left bank coild which seem fine, they are doing the right bank tomorrow so am hoping they will crack it as currently the bill is almost £350!! thankfully the garage I bought from have given me a months full guarantee and are paying for the repair which is refreshing

They've also checked the battery which according to them is weak! I wonder if that is a contributory cause ?? I will put a new battery anyway, hopefully they've sorted it tomorrow.
Such a shame these lovely cars have this fault

 

It could be something as simple as water in the spark plug wells. The seals over the coil packs tend to leak with age, and if water gets splashed up from the road, or coolant leaks from the overflow, etc... it goes right into the wells and causes the misfiring.

 

Interfering Brit here... Keep it simple...fuel or ignition.

Spark plugs rarely give issues even if you have a coil problem. If you have a random misfire is it ok when cold and comes in when warmed up? Check for obvious air leaks or water leaks.

Ahh no fault codes... Yep been there too. You might want to try getting a new coil and starting it one end, swopping it until you loose the misfire. At least this will identify the issue but you will/might as we'll replace all the coils as in this case this will be what you will end up doing. I had this with my s type and xkr.

Sounds like the garage is doing the right things. By the way don't think it's a Jag problem...it's all part of our glorious globalisation! Gearboxes for later xk is the troubled zf and it plagues BMWs too. The coils are Denso, used by Ford in the uk and US so poor old Jag are hit by indifferent parts quality.

Codes are worth checking with a scanner. Don't use a Jaguar distributor but a specialist independent Jag garage.

If you shop carefully, you can stay OEM or at least high quality at a sensible price.

I have to accept they are a high maintenance super car...still great value and lovely.

Oh now I'm in trouble ....

 

Thanks for the replies folks apparently the plugs were knackered garage said probably from new, it's had a good service history and only 63k with all mot's and garage bills, they've checked the left bank coils and they said seem fine but right will be checked*tomorrow , he reckons water has indeed got into the area and thinks I might need at least 4 new coils it's intermittent but from cold and hot but goes away from time to time but all of a sudden returns.

Once again thanks for your help and responses

 

Garage says two coils were broken and needed replacing am picking her up tomorrow
Autopics Rustington /Littlehampton want me to text drive to make sure am happy, I will put a new battery soon just to eliminate that possibility ?

 

Yep, good old coils...

 

I've replaced 2.....1997 2003 Jaguar Vanden Plas XJ8 XJR XK8 XKR V8 Ignition Coil New | eBay

 

Its the coils you need all 8 of them, mine did the same, no codes or nothing, had me stumped.

 

Seems you're spot on there

I've taken from the Garage Autopics Rustington this morning and guess what no real change! despite the Mechanic's efforts he had a good look at all coils and tested them and reckons the others don't look too bad he replaced just the one coil and replaced all platinum plugs,diagnositc etc £381 ouch now it seems a bit better but still not purring as it should

The one coil was £40 so if anyone can help me find 8 decent coils I would appreciate it
He would be happy to fit them as he's just as baffled why his efforts haven't made any difference!!

 

I have an Ebay Jaguar breakers who is happy to sell me some good condition coils to replace all 8, but his reply to my offer was he couldn't guarantee it was the coils causing misfire and could be wiring harness,air flow meter,lambada sensor,cam sensor,VVT?

My problem is obviously a unique one because no fault codes were found! from V8 specialist
who done diagnostic and changed all plugs, and one faulty coil but still no change and engine still judders at idle and at around 50-60mph under hard acceleration the garage who done the work has a great reputation.


Autopics Classic & Sports

 

I keep a spare new coil in the boot of my xk8...never know when that sucker will need a new one. Upon acceleration, my xk8 knocked pretty bad with lots of little vacuum leaks, but never misfired. Hope those coils cure ya!

 

Hi All I've been living with this frustrating,annoying, soul destoying intermittent misfire since trading in my lovely 3.0 manual 6 weeks or so ago
My Mechanic who's a v8 specialist has run another ful diagnostic and cant find any faults, checked for vacum leaks and found zippo he suggests I take it to a main dealer or someone else who's familiar with Jags!! am disappointed to say the least that he's given up and obviously want to try and avoid main dealer prices!

Plugs have been changed,one coil, and fuel filter,injector cleaners etc still lumpy sometimes then runs like a dream for a day or two then rumble stutter returns!
Anyone know of a Jag mech in the South of England?