Hello jag lovers! My XJ6 S2 cant keep idle. After I start the engine, to keep it running I must push the accelarator otherwise the engine dies. It is impossible to drive the car cause from the moment I am trying to put a gear it is turning off. Any ideas? Thanks in advance.
I’m not sure but sounds like there isn’t enough fuel coming through if it was a modern car it be a man sensor but to my knowledge these don’t have one but if increase revs is keeping it running check the choke and how does she sound when she’s running lumpy ruff that sort or stuff but check fuel supply and spark is good always where I’d start myself on any car
Hello back Dimitris, it won’t be the MAF sensor but the idea is mixture, and I assume your fuel delivery is working well enough. It revs up, so there is fuel at the floats.
Does it start well? If so, your AED (the small extra carb for the choke) must work. And air leaks might be excludable to a degree.
Now, what is your idle speed? If the idle speed is too low it won’t have enough torque to keep up. Either the mixture is too lean, about which I can’t help you due to my lack of carb experience, or the engine doesn’t get enough air. Also not impossible is that the engine chokes because there is a leak at a carb needle and it dies from overfueling: does it produce black smoke?
//a carb could be stuck (old gas, etc.) and overfueling. You add air and the mixture becomes less rich as the needle didn’t move but the throttle did. That explains good starts and bad running, at least it’s a good chance.
I assume the car was standing all winter? You might want to take the air filter off and check for anything visible. If the fuel pumps are diaphragm pumps, wait until the clicking stops, look at the carbs and see if they leak if somebody chimes in and says that’s conclusive.
The workshop manual adds general tune to the troubleshooting. Do all cylinders fire? Does it change things for the better if you switch tanks? Does it turn over nicely when starting (I imagine so as you would have mentioned all that).
If nothing serious seems to be amiss - noise, smoke and all that - and your neighbors can stand it it might be worth to set or keep the idle somewhat higher so it doesn’t die and see if you can bring it back down when hot.
Confusing enough but you might start at the carbs.
Spark and fuel seem available. You‘ll get her running, rather she does run which is a good start!
Good luck.
David
I agree with David, we need a bit more information. Have you tried using your left foot to step on the brake pedal and then keeping the accelerator depressed to raise the RPM can you get the car into gear and drive it?
Dimitris,
with a warm engine idle in N or P should be around 750 RPM, falling in D or R to around 650 RPM. A healthy and warm engine will take this.
With the cold start enrichment I typically adjust to 1100 in N or P before I put it in gear.
Like David I’d suspect an engine/carb related fault. Yet, it might be that something is wrong with the auto box increasing drag in gear. Did you check all possible gears? Can you “help” the engine with light throttle?
Good luck
Jochen
75XJ6L 4.2 auto (UK spec)
drEx,
Does your S2 XJ6 have carburetors or was it one of the later ones with fuel injection?
Paul
Hi Paul is 1975 model with carburetors.
Hello Jochen!
Ideally the idle was 750-800rpm and with gear was falling to 650rpm but now if I dont push the accelarator it dies and when I’m trying to put gear it dies directly.
Thank you for your reply
I tried it Robin but with no luck !! I can’t get the car into gear.
Hello David!
First of all I have a manual choke kit instead the AED. The pumps sound good and it starts well but if I don’t push the accelarator it dies. When it goes below 1300rpm it dies.
And you are right I have a lot of black smoke so that the neighbours and me either can’t stand it!!
The jag was standing in a cold garage all winter.
I didn’t notice any leak of gas…
I 'll check the carbs as you advised me and I’ll take the air filter to take a look.
What does the black smoke means?
Unfortunately I have free time only at weekends so I have to wait till Saturday.
I’ll inform you if I find something.
Thanks a lot!
Dimitris
The black smoke means that you are running too rich. (Black smoke means too much fuel, blue means oil, white is condensation or water).
I think you are lucky given the circumstances. When you take the filter off you will probably see the inlets of the carburetors and I am sure that one of the three (I assume the choke kit manually activates the AED) needles is either stuck open or binding. Or dirty, and if none of these apply then excessive fuel pressure or so. Jochen and other SII owners and earlier have to take you from there.
All your other settings seem fine, and why wouldn’t they. When you have the problem fixed you might want to take the spark plugs out and brush the soot off.
Good luck on the weekend!
David
**
As David says; you are running far to rich, Dimitris…
…which explains why it dies below 1300 rpms. The xk is very tolerant to running fat, but there are limits!
Ensure the manual AED is set fully off, and clamp the fuel hose to it. This will eliminate fuelling from the AED - and the overfuelling should stop, which will confirm that the carbs are working OK, or not. Then you can attend to the faulty component…
Frank
xj6 85 Sov Europe (UK/NZ)
**
Dimitris,
this doesn’t sound too complicated. As you describe it you can exclude the gearbox from the list.
Your car is obviously running rich. Get it started, warm up the engine and then pull the rubber tubes from the aux carb and block the intakes. Then check the balancing and tuning of the main carbs. Chances are something is stuck there or gummed up. Correct everything and tune the carbs. Then reconnect the aux carb. If it continues to run rich - and in particular, if the main carbs have shown no fault, the problem is within the aux carb. If it is cable controlled the only cause of trouble I’m aware of is a sticking or sunk float flooding the aux carb and enriching the mixture.
Maybe, before getting into all that you could check the plugs. If 3 and 3 are different, it’ll be one of the main carbs, if they are all similarly sooty, you might check the float chamber of the aux carb directly.
Good luck and keep us posted
Jochen
75 XJ6L 4.2 auto (UK spec)
Stromberg carbs? Have you checked the vacuum diaphragms? No idle is usually the sign of a vacuum leak.