Anyone got thoughts on this problem?… This Jag has run quite well since I acquired it until late last summer when I needed to put it winter storage - I went to start it and it seemed to start with only maybe 4 out of 12 cylinders firing - throttling it stalled it out - kept trying and eventually it wouldn’t start at all - put gas treatment/additives in next day - tried to get it going again - same very rough start - left it running that way for a few min’s and all of a sudden it smoothed out and ran just fine - took it to storage… trying to get it out of storage this spring and I’m having the same issue with rough start/stalls - so far I haven’t gotten it to spontaneously cure it’s self again - been trying on/off over 3 days - (leery of putting in any more gas additives).....

 

'86 XJS coupe - less than 70,000 miles on it.....

 

So it ran fine and you put it in storage for several months and then it wouldn't run?
This is completely normal. You have a very high compression engine with fuel that has turned to crap after sitting for so long. It loses most of its volatility and the ethanol begins to gel up.

So the fuel won't ignite because it has lost volatility and it can gum up your injectors. If you plan on putting your vehicle in storage for long amounts of time ALWAYS put a fuel stabilizer in it and then put gas in it and run it. This will mix the stabilizer throughout and insure the lines and injectors are protected as well.

You could also drain in. If you put fuel and stabilize it fill it up to the top to help prevent the tank from rusting where it is exposed to air.

the mileage is irrelevant, bad gas is bad gas. 10% ethanol gas can go very bad in only a few months

Run a good amount of high quality injector cleaner through it ( use up at least half the tank) and then add stabilizer like I suggested.
Do you just not drive it in the winter due to traction and the v12 taking 4 centuries to warm up?

 

Better yet, ALWAYS turn it on at least once a month. Cars in general do not do well just sitting around, as gasket seals and moving parts do need the lubrication that moving fluids provide. Otherwise seals and what not begin to rot and the fluids themselves start to break down.


It would be more ideal to run the vehicle after letting it warm up to normal temperature if it has been sitting around for a while. If this isn't possible (because it's snowing, etc.), then at the very least turn it on and let it warm up to temperature just to get those fluids moving around the system.


And add a fuel stabilizer as was well suggested.

 

As I said in my posting - I did put additives in the tank before putting it in storage - both stabilizer & injector cleaner - also ran it (once it started running smoothly) for about 30 min's getting it to storage and it ran quite well for that 30 min's... also - the problem didn't first occur after it had been in storage - it first occurred in late summer after being out all summer and being driven a bit - this is why I'm asking for advice/thoughts - because I did as suggested - stabilizer & injector cleaner - (BTW - I also have an '88 with no engine issues - I do not drive them at all in winter because of salt).....

 

The way you've described the sequence of events is confusing to me but if everything was OK until you took it out of winter storage then a fuel problem is a good place to start. Or as good as ay other. But it sounds like the problem....rough running.... occurred *before* storage as well, yes?

My *personal* experience is that fuel doesn't go that bad that quickly but it's possible if the storage conditions are right....or perhaps I should say wrong. Was the car stored in a climate controlled environment?

I would pull the fuel filter and empty the contents into a clear container. What you see (or don't see) will dictate your next steps. Give the gas a sniff test as well. In my experience, if it is stale enough to cause the problem you're describing, which seems fairly severe, it'll smell terrible.

Of course there are many other possibilities that might explain the very rough running: an old fashion ignition fault (perhaps rodent chewed spark plug wires?), a problem with the fuel injectors (perhaps not related to fuel age...possibly a harness problem), a poor ground or other wiring/electrical fault....the list goes on and on.

Have you checked anything so far, even if only visually?

If it turns out that fuel isn't the problem then it's a matter of a long checklist and picking a place to jump in.

Cheers
DD

 

The problem started last summer prior to my putting it in storage... and the problem occurred again as I was trying to get it into storage... both those times it eventually cleared up on it's own and it ran fine after many rough start-ups... now it's doing it again as I'm trying to get out of storage... since I put stabilizer and injector cleaner in when I put it in storage, I'm leery of adding even more... I'll check what the fuel filter contents looks/smells like.....