My Daily Driver XJ6 has Another Misfire! - Is it Fuel or Ignition?

My usual daily driver, a 1975 Jaguar XJ6 has developed a misfire. It happened the day after the previous video when I replaced the alternator. Is there a connection? Did the high voltage damage my 123 ignition distributor? I hope not!

#jaguar #xj6 #dailydriver

[mercedesvan-doors]

I've spent a lifetime working at old Jags and it's great to see someone taking time to understand and help their car. These cars can have complexity in their systems and I would suggest the following. Number one is consider changing to a waterless coolant, it destresses the ageing cooling system by not raising pressure when hot and never boiling, number 2 check and clean all the various electrical earth points round the vehicle, helps destress the electrical system and in one this age swap out all the heavily used relays for new, the lights, wipers etc. In relation to a misfire start with a compression test, if it's comp is good then try ignition. I noted you said you washed the car before the issue started, did you use a pressure washer and get water into or around the ignition parts, it sounded like a moisture misfire. Thirdly drain and flush out the fuel system and replace filters. I really hope this car befrends you because a good Jag is a thing of love and beauty, a bad jag will break you.

[RobinHill]

Coil! Change the coil. Got stranded with mine when out driving on a hot day and the engine started misfiring and losing power - limped home. I changed the old (1988) Lucas coil for an Accuspark sports coil and now it runs like a sewing machine. I never realised that oil coils will fail when they get hot, but apparently this is a 'thing'.

[jaguarrroman]

And the third possible and the worst reason of misfiring is bad compression. It doesn't look like bad compression in this case, still it is worth mentioning. Good luck, Adam!

[e]

I smile when I see Adam driving with a worried expression and the gears in his brain trying to make a diagnosis. Is it not an experience we have in common (or will) among XJ6 owners !
I hope, Adam, you will find the problem quickly, but with your knowledge and patience, I am confident you will find a solution.
Thank you so much for all these interesting videos. You helped me more than once!

[johnmoruzzi]

I think the problem with the XJ6 is revealed right at the end of the video… it’s not happy that you’re now infatuated with the shiny red Rover 3500 V8 and wants some attention and appreciation !

[brianwhittington]

It does sound more electrical than fuel, which usually shows up more at high temperatures, high revs, or under load. Problems with Lucas components on British cars have been a well known issue for years here in the UK, they're the first checkpoint we look at. One thing often overlooked is cross firing through the HT leads touching each other, or earthing out to metal due to the old insulation breaking down. Early Rover V8 HT leads were notorious for crossfire issues, and there was a proper factory layout, with lead spacers to avoid it happening. The best way to check is in darkness, see if there is any feint glow where leads touch each other etc. A temporary fix can be to spray a mist of WD40 over all the leads and cap, until fitting a new set. One other thing to check is the optical or magnetic triggering unit in some Lucas distributor models, and that the plastic flash over shield that stops the risk of stray HT voltage feedback to the triggering pick up unit is in place. Check for dirt or tarnishing of the components, and for any sooty looking track marks in the distributor cap and rotor arm. Often, poor intermittant contact between the rotor arm and the centre carbon brush in the distributor cap will give those odd misfire symptoms.

[williamendres]

Thanks for taking us along as you troubleshoot this issue, very interesting!

[dantiel]

I put an electronic after market distributor in my mk. 2 and it had very late advance curve it ran like a dog I put the old points unit in all good also watch out for bad rotors that fail when hot

[bobcooke]

Wishing you success in resolving this issue or issues 👍🙂

[TMGJ]

Both driving with and without Alternator it appeared the misfire when you took a turn. That suggests possible fuel delivery issues.

[charliecoco]

Maybe there is now dampness in the dizzy cap. Causing erratic sparking.

[sitaylor]

Great car i had 1 when i was 18 so a long time ago now but it was a very nice drive

[mikehill]

USA, Thank for the pictures and the autos. 😊

[bobstride]

I wonder if it could be the condenser, I had something similar to your issue a while back and I had changed the condenser for a new one which was faulty straight out of the box, I put the old one back in and it fixed the issue!

[landydrvr]

I had a 78 Series 2 XJ with a Camaro Tuned Port injected V8 and had a similar problem. I had rusty gas tanks and the rust would eat up the high pressure pump and also clog the injectors. It only showed itself when under high load, going quick or uphill. I know yours is not injected but a questionable gas supply will do that.

[hueyhoolihan]

any diagnosis should encompass the fact that when cold there is no problem. IOW, if whatever is being considered as the culprit should also be capable of hiding itself when the engine is cold.

for instance, if the problem is with the distributor, it would seem unlikely that it would fail once the engine reached running temperature. water in the fuel? same thing.

OTOH, electrical shorts (especially in ignition wires) are often only made manifest only at higher temps. but if the engine is missing on more than one cylinder, than it may be the cap or rotor.

[parrotraiser]

If you are unlucky, trouble-shooting by swapping can lead to unfortunate and confusing results as the culprit destroys formerly working parts. The most extreme example I know was from the days when computer disks had removable platters. After a head strike, (a hazard in those days, which could create further strikes by closing the gap between head and dsk), by trying platters on other drives, and other platters, a consientious but not terribly bright operator managed to destroy every drive and all the disks in the installation.
I hope it was just watery fuel in this case.

[truxton]

Misfires like this is usually ignition related.

[nigelbond]

Hey Adam. Great video. I need to preface this by admitting I know very little however my XJ6 series 1 had a similar lumpy misfire which turned out to be an irregular fuel flow through the carbs. I’m probably way off the mark though 😂

[jeffharrison]

That's a head scratcher. Good luck.