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.

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'.

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

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 !

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!

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!

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

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

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

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

USA, Thank for the pictures and the autos. 😊

Misfires like this is usually ignition related.

Wishing you success in resolving this issue or issues 👍🙂

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!

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.

That's a head scratcher. Good luck.

@LivingWithAClassic

Жыл бұрын

Thanks Jeff!

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.

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.

That's always the question. Fuel or Electric.

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.

@LivingWithAClassic

Жыл бұрын

Issue was there both cold and hot. Initially just hot but the next day it was there cold too

Adam, thanks for another really useful video. I too have a ‘74 XJ6 with a 123 Ignition & three weeks ago exactly the same misfire symptoms appeared, almost overnight. Like you I’ve swapped the coil to no avail and also the plugs and leads. One thing I’ve found is that the plugs keep getting sooty, despite the carb settings being good and floats & needles all ok. What are your plugs like? I’m wondering if an issue with the 123 distributor could cause this symptom. Good luck & I look forward to the follow up.

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 😂

@T16MGJ

Жыл бұрын

Like you, I believe it is fuel delivery issues.

If it came on slowly then missed headgasget,if all at once then,its ign.

@LivingWithAClassic

Жыл бұрын

It was from one day to another so came on pretty quickly

Bad earth connection? I've seen that make all sorts of gremlins sppear from misfire to bad acceleration. That new fuel comment is interesting...how is that stuff where you live?

It could be a fuel issue. Check the jet diaphragms, the floats and the float levels.

@LivingWithAClassic

Жыл бұрын

Does have jet diaphragms and I don’t think the float levels change from one day to another. However water in the fuel is more likely

@Thereishope664

Жыл бұрын

@@LivingWithAClassic Just a thought, My E-Type had a mis-fire and it has the 123 like yours with Magnecor leads(wires) and new plugs. I was mystified and once I'd overhauled the carbs with new jet diaphragms, spindles, floats, needles etc the misfires completely disappeared.

did you adapt the earlier cam covers to fit the XJ cylinder head? I wanted to use them on my 420g but its got an XJ6 S2 head and i had to use its rocker covers instead since it didnt have the holes to attach the circular blanking plate thing from the original head. I prefer its raised jaguar lettering over the sticker

@LivingWithAClassic

Жыл бұрын

I have a series 1 engine in this car at the moment so that's why I have those cam covers.

very interested to know please the Bluetooth App you use that monitors the gauges?

@LivingWithAClassic

11 ай бұрын

It is the 123 Tune app. It goes along with my 123 Tune+ distributor

These engine dont like 98 octane fuell, in my 4.2 i use to put 98 and the car was failing in acceleration i start to use only 95 and the prob gone

What app are you using on your phone for the instruments?

@LivingWithAClassic

2 ай бұрын

Its 123 ignition tune+. I use it to control my 123 ignition

If my XJ6 had issues like this I'd be dead in the water. I don't have an extra distributor to swap in and out...

@donswork3059

Жыл бұрын

So I'd be hoping it was a fuel related issue which I could find.