XJ40 stalling

I recently purchased a Jag XJ40, 4-litre auto (1991). I didn't notice any problems on the first day I got it, but twice today I've had a problem where
I start the car up and it ticks over fine (though the car does judder a bit more than I would expect - timing out perhaps, or maybe sparks need replacing? it does idle at about 750 rpm - is that too low?) but as soon as I shift the box into reverse or drive it stalls. This happens 3 or 4 times and then it sets off fine, and hasn't stalled at traffic lights or anything.
The oil pressure in the car seems fine (usually just over half way on the dial - 5-ish), temps OK and there are no warnings reported by the ECU. I followed the instructions in the manual for checking the gearbox oil level, but couldn't get a very good reading.. that is, after I clean the dipstick and push it in/pull it out again, there's a thin film of oil all the way up the stick (past the "hot" marker), no matter how many times I repeat the measuring process. I'll have to have another go at this, but the gearbox seems to work fine after the initial stalling episode.
Two things I am wondering about - when I bought the car the guy at the garage said that when they got it they had to change the battery and they got standard cheap one from their regular supplier.. indeed, the central locking didn't work at first, but it had been sitting for 4-5 weeks at the garage and after I drove it the 100 miles or so home and took it around town a bit the locking suddenly started working and it's worked without fail since. However, do Jags have a heavier duty batteries fitted to them normally, given all the electrics they have in them? If that is the case, is it possible this is the cause of the stalling (OK, maybe that's daft since it starts first time and it's only when you shift it into gear that it stalls, but I have to ask as I'm no mechanic!).
The other thing is that I thought I had read somewhere in a bit of documentation that came with the car (there was loads of stuff!) that the car would take 95 ot 97 RON unleaded.. but when I was going through the manual I found a bit that said "use only premium unleaded".. isn't "premium unleaded" the 97 RON stuff? could that cause the stalling maybe?
Any ideas on this stalling issue, or for that matter - how to get a clean reading from the auto box dip stick!?
Thanks Ian
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The transmission should be checked with the engine at idle and after the car's been driven 5 or 10 miles so the box is HOT. The correct level should not exceed the upper mark, if so it's overfilled and some should be drained.
Stalling - too soon to tell. Could be incorrect idle speed adjustment, worn spark plugs, worn ignition cables or a vacuum leak. You're going to have to do some work to eliminate the most obvious causes i.e. spark plugs etc.
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ok thanks.. I'll check that again.

I was going to do the basics like sparks myself, but I think there are a few bits that woul dbe worth checking out so I've booked a service and will take it from there.
Thanks IanW
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ings I am wondering about - when I bought the car the guy at the

IO have a '94 and the security system draws enough current that I cannot start the car if it is left for 5 weeks without running.
I would suspect that the battery is the culprit.
Don't think the battery has anything to do with the stalling.
750rpm is an adequate idle. Richard H. Kuschel "I canna change the law of physics."-----Scotty
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the
town
is
since
start
are the proper batteries for the Jag kind of longer than the average car? the reason I ask is that the one that they put in there doesn't look like it fills the slot completely.

aye.. I've got it booked in for a service thursday, so hopefully that will sort out the stalling.. now that the central locking is working properly (which was the only electric bit that wasn't, I think I'll leave the current batt in and see how it goes.
Thanks
IanW
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Dear Ian,
I have yet to find a Jaguar with an alarm that did not drain the battery during storage. Even Jaguar was aware of this an noted in the manual "For storage unhook the battery". I believe storage is considered 2 weeks time.
On occasion the idle control valve will lose its calibration with the battery going flat. This might not be your problem, but I highly suspect it. It is a relatively simple process to reset your idle valve and find out. Also there is a little single wire temp sender near the front of the engine; clean the connector and blade.
BD
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I had it in for service yesterday and the mechanic found that the air intake pipe hadn't been fitted properly and there was a gap there. He also cleaned out various bits. He also mentioned that temp sender and thought it is probably what's causing the fluctuation of revs when the engine is idling cold, so one of those is on order :-)
Thanks Ian
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