what to look for v12 misfire?
Discussion
im in the process of buying a xjs v12 cabriolet that thas been off the road for some years.
the body is not to bad and i have a good idea of the general condition.
however i could not hear it running as it was flat but the owner told be that he had it going last week but it was missing a little im goin back to have a look on sunday when its going any ideas what i could be or common problems?
also any pointers as to what to take a look at maybe a sort of buyers guide?
may thanks.
oh its a 88 f plate with only around 50k miles
the body is not to bad and i have a good idea of the general condition.
however i could not hear it running as it was flat but the owner told be that he had it going last week but it was missing a little im goin back to have a look on sunday when its going any ideas what i could be or common problems?
also any pointers as to what to take a look at maybe a sort of buyers guide?
may thanks.
oh its a 88 f plate with only around 50k miles
If it's been stood for a while it could be a good number of things. These are the ones I've usually found
Dirty or fouled plugs
Seized advance mechanism in the distributor
Non functioning vacuum advance capsule on the distributor
Old plug leads arcing
Weeping injectors due to fuel residue after being stood
Ingnition amplifiers, particularly on Marelli ignition cars
The V12 is a fairly basic engine, it's just theres a hell of a lot of it. If yoy are going to do the work yourself just be careful and methodical and you shouldn't have too much difficulty.
Regards
Ric
Dirty or fouled plugs
Seized advance mechanism in the distributor
Non functioning vacuum advance capsule on the distributor
Old plug leads arcing
Weeping injectors due to fuel residue after being stood
Ingnition amplifiers, particularly on Marelli ignition cars
The V12 is a fairly basic engine, it's just theres a hell of a lot of it. If yoy are going to do the work yourself just be careful and methodical and you shouldn't have too much difficulty.
Regards
Ric
Be careful they will be very tight, work them too and fro with lubricant, WD or some such, so as not to strip the plug thread in the head.Take your time, there is no rush .Make sure they go back easily. It is just as easy to cross thread the back plugs and those under the airco pump. Take it off the motor but do not disconnect the pipework. That should give you enough room.if you are brave enough take the cap and leads right off and look at the rotor. Its probably full of filigrie, a blueish deposit at the tip of the blade. Then clean off the contacts inside the cap, then remove each lead separately and clean out the debris in the locating hole. This too will probably be full of the blueish deposit.I hope I have spelt filigrie right!Good luck
had a little time to look at ut yesterday and allthough a bit of a pain the plugs can all be removed and replaced with out taking anything off.
much better after a clean and regap as they looked almost new.
still not quite right though so next stop to look at the dizzy. next time i get 5 mins.
much better after a clean and regap as they looked almost new.
still not quite right though so next stop to look at the dizzy. next time i get 5 mins.
ive been busy with some welding for the last few days but will be back on the misfire next week.
iv put an injection cleaner in the tank but have not had chance to give it a good run . need to pinch some trade plates then i can take it out.
would you recomend removing the injectors to clean them?
iv put an injection cleaner in the tank but have not had chance to give it a good run . need to pinch some trade plates then i can take it out.
would you recomend removing the injectors to clean them?
If you take the injectors out you will need to replace all the little rubber seals that sit underneath them. Use a mechanics stethoscope (or a long screwdriver) to see whether they are firing first when the engine is running. A weeping injector shouldn't really cause anything more than a bit of rich running, however a stuck one will need looking at.
The ignition system has always been the cause of troubles in the V12's I've had. Run the car in the dark and look under the bonnet. If the plug leads aren't fairly new, the engine heat will have fried them and there will be a miniture lightning storm going on from all the arcing.
With care you can get these so smooth you can balance a coin on the engine while it's running.
The ignition system has always been the cause of troubles in the V12's I've had. Run the car in the dark and look under the bonnet. If the plug leads aren't fairly new, the engine heat will have fried them and there will be a miniture lightning storm going on from all the arcing.
With care you can get these so smooth you can balance a coin on the engine while it's running.
ok more fun today finished my welding and free'd up the rear calipers so i whiped out (yeah right) the plugs on bank a again. all around 175 psi compresion. all sparking and all the leads are good.
but the one under the ac compressor is not firing. when you unplug the injector it makes no diffrence.
so off with them tomorrow.
on another note any one no where i can get a front center valance pannel from mine turned into dust.
p.s if i get chance ill get some pics up tomorrow.
but the one under the ac compressor is not firing. when you unplug the injector it makes no diffrence.
so off with them tomorrow.
on another note any one no where i can get a front center valance pannel from mine turned into dust.
p.s if i get chance ill get some pics up tomorrow.
If its just green and dirty try cleaning it first with Autoglymn hood cleaner. Really scrub it with a nail brush then blast it with it a pressure washer working from front to back. It may need doing 2 or 3 times but you will be pleaseantly surprised at the outcome. If its` a no hope-r its just your elbow grease lost.I`ve done many a hood this way.
hoppo4.2 said:
if you have one that would be brill.
also if any one has or knows where i might get a set of carpets and a pasanger side seat in grey. as well as a hood ? blue or black
on another note it's running on all 12 at last.
fingers crossed it will pass its mot tomorrow
Now you got all 12 working - i'll let you know a little story about a colleague of my dad's years ago. S11 XJ. He managed to drop a valve through a piston, but it still managed a few weeks running before he lifted a head after various other diagnostics. Apparently it wasn't running too badly by all accounts.also if any one has or knows where i might get a set of carpets and a pasanger side seat in grey. as well as a hood ? blue or black
on another note it's running on all 12 at last.
fingers crossed it will pass its mot tomorrow
fatboy b said:
Now you got all 12 working - i'll let you know a little story about a colleague of my dad's years ago. S11 XJ. He managed to drop a valve through a piston, but it still managed a few weeks running before he lifted a head after various other diagnostics. Apparently it wasn't running too badly by all accounts.
I can well believe that. I had a six run on the five it had left after chucking a rod out through the side. I had another that was on 5 cylinders for a long time after burning a valve.Sometimes on the V12 you can only tell a misfire from the exhaust sound.
ok back from the MOT after 5 years of sitting out side on some drive. indicator tell tale lamp not working. and excessive hand brake travel. not bad.
oh and a tyre so all will be well tomorrow.
the hood has 2 big holes in where roof tiles fell on it during its time sitting around. so will need to be replaced. also the rams that move it up and down are also shot.
oh and a tyre so all will be well tomorrow.
the hood has 2 big holes in where roof tiles fell on it during its time sitting around. so will need to be replaced. also the rams that move it up and down are also shot.
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