Hi all,

Something's just happened that's got me stumped. The XJ has just been serviced (Cheltenham Jaguar two weeks ago), and I was off for a half-hour journey this Friday, so dropped into the local (quite cheap) garage to put a bit of petrol in. I'd actually just commented to a friend who was with me how well it was idling when it started up - it's always been quite good, but post-service was running like new.

Anyway, I put the petrol in, then started up to get going. I reached a crossroads five minutes down the road, then had to stop for the red light. Suddenly the car was having serious trouble idling - it felt like it was trying to stall while I had my foot on the brake - the entire car was shaking, and the RPM needle was dipping below the usual 7/800. I got very worried - it's had about £1200 spent on it in the last six months and is running better than ever, but this seems pretty serious.

Starting to pull away was interesting - it juddered and power was intermittent by the second - it was juddering away pretty unhappily. I pulled up in a lay-by just after this to check it - sure enough, the engine block was shaking away, but it seemed to rev up alright - anything over 1500RPM seemed to get rid of the shaking.

So I carried on, as it was quite a fast road and I could it at 50 and see how it did. It got progressively better, and starting up at the other end to come home was much less worrying than it had been.

I started wondering whether it was the fuel, so I went and put £20 of Tesco's bog-standard petrol in, and it went fine! Beautifully in fact. But I started it up again Monday morning and the shake was back in a big way.

Is this bad petrol causing the engine to run lean combined with the new fuel filter? Or (as I'm still waiting to be paid for a lot of work) as I haven't filled up above half way recently, is it having trouble with the gunk at the bottom of the tank?

It seems a lot like a misfiring engine to me. It's not using significantly more petrol, but it sounds like a tractor when it pulls away, and there's the idle trouble - Park is bad, but Drive is much worse, as is Reverse. Then again, I'm no expert.

Does anyone have any clue? I've got some videos of the engine on my phone which I'll try to post up, but what's the solution? Spark plugs? Do these fuel additives do anything beneficial? Or is it something more serious?

Thanks in advance,

Alasdair

 

Sounds like one or more cylinders mis-firing, diagnosis may take a little time.
With engine idling (roughly I assume) , and with coil cover removed, disconnect one coil pack at a time and listen for worsening effect if any, with a little luck one disconnection will not make a difference so you can isolate a potential problem to a particular cylinder.
Check all plugs are tight also. I had a similar problem traced to a loose plug - as the engine got warm it went away due to hot metal expansion I presume....
I can't recall if the X300 has OBD2 codes, if so this will save you some time....

 

There are ODB2 codes, but from what I've read here, they are slow to report a misfire. The most common report I've seen is coil failure (it has to happen sooner or later).

-HC

 

Obviously you might have got bad or water contaminated gas, BUT, as you have been told already, these cars are having a lot of reported coil failures these days. I would go with Kyle's plan and read Doug's thread on "Heads Up on X-300 coils"
Good luck and keep us updated.

 

Hi Alasdair,

One or more bad coils could cause your symptoms, but the timing of having just added petrol is certainly suspicious. It might be worth disconnecting the fuel feed line at a convenient point: just ahead of the fuel filter might be best, but just ahead of the fuel rail would be more convenient. Run the fuel pump to evacuate a couple of gallons of the fuel tank's contents into a petrol can or other suitable container. Agitate the petrol can, then pour some of its contents into a clear glass or plastic container and allow it to decant. If the petrol you received had a significant water content, your new fuel filter will need to be thoroughly dried or replaced.

You could also revisit the local garage and ask them to show you the water level in their fuel storage tank. In the U.S., stations are required to measure the water level in underground tanks using a long graduated rod covered with a special paste that changes color when it comes into contact with water. By law, when the water reaches a certain level, it must be evacuated. I assume similar standards exist in the U.K.

Cheers,

Don

 

Thanks guys! This forum is the absolute saviour of owning an old Jaguar!

I've run a bit more petrol through and it's definitely a misfire, maybe just a coincidence - I had head coil packs are temperamental, so that makes sense. They're still the 1995 originals, so it's probably time to move on. Now to find out which one(s) to replace somehow, and get some ordered. I'm going away for a week tomorrow, so I'll get on it next week and let you know how it goes.

Thanks again!

 

READ DOUG's POST before changing all your coils, as I think you might be hinting at. The replacements are not as good as the originals in general!

 

Thanks for all the advice - I've just got it all sorted out. Oddly, for a problem that took about three weeks to solve, it was a £30 fix. As suspected, it was just a coincidence that I'd just filled up, and ignition coil 2 had packed up. I tried to find good coils, but failing that for a week and with a drive to Scotland coming up I hoped for the best and bought one for £25 from British Parts (with one spare for the boot). Runs perfectly! I'll see how the cheap coil goes (or rather how long until the cheap coil goes!)