Sovereign V12 Engine Dramas - any idea?
 

Hi guys,

My old man and I have recently bought a 1986 Jaguar Sovereign V12 in immaculate condition, inside and out (so we thought). Don't get me wrong, the car is gorgeous, and the motor was strong and healthy when we picked her up. But recently, she's developed a problem.

Whilst driving home the other day, the motor developed fairly substantial, frequent knock, and the motor wouldn't rev past about 1500rpm and wouldn't drive faster than about 30km/h. Pulled over, turned the car off. Checked oil levels, and other general first-check items. All seemed well, so started the car, and it purred like a kitten. Ran and drove fine without so much as a grumble for 30minutes. I assumed it must have had something caught in it's throat.

The next day, driving it out and about, the knock came back, but very infrequent. Only every few minutes it would knock once, and that was it. No power loss, but very low oil pressure at idle (VERY low, almost 0). Quickly switched it off and once again, checked the oil, ducked underneath to check for any obvious signs of oil loss etc... Nothing. When I switched it back on, it was running like a chauff cutter. The motor was very choppy, wouldn't rev at all, and wouldn't accellerate.

We had it towed home, as I didn't want to risk anything serious happening (If it hadn't already). Lifted it up, drained the oil, did a filter change etc (Oil looked fine, clean, new, same as filter) ran an oil flush through it and re-drained. Refilled, and let it sit. Gave it a quick start, and it was still choppy, very rough and nasty sounding.

My question is, obviously, has anyone had similar experiences, or does anyone know what I might look for to find the problem? I dred a rebuild on this engine, as it'd be a big hit to the back pocket, but if I can't find the problem, that will have to be the answer.

Any help would be greatly appreciated.

Thanks,

Matt


PS - I am having troubles getting this meesage to post, so if it has posted numerous times, I apologise.

RE: Sovereign V12 Engine Dramas - any idea?
 

First, don't worry about the "low" oil pressure at idle. That is where the v12 idles. I drove me batty with them 1990 XJS to sit at a traffic light and watch that guage sit at nearly "0." This is normal.

Knock is not normal. If the engine settles down occassionally, it tells me it's nothing serious. I'll venture a guess it's something in engine management but need more details to be of any real help.

RE: Sovereign V12 Engine Dramas - any idea?
 

Given that you just got the car anyways, it might be a good idea to start doing some basic tune-up procedures Sounds like the low idle oil pressure is normal, so you can shift your focus......new spark plugs (+ wires?), air filter, fuel filter, etc. Sometimes the basics will do it. I wouldn't freak out about a "rebuild" yet.

RE: Sovereign V12 Engine Dramas - any idea?
 

forgot to mention, I would love to see some pix!!

RE: Sovereign V12 Engine Dramas - any idea?
 

Thanks for the replies guys, we've done a normal tune-up on it. We did oil, plugs and filters etc when we got the car, and when the drama started we did the oil a few times trying to pinpoint the problem.
Thanks for the info about the oil pressure at idle though, thats a bit of weight lifted off the problem.

I will upload some pics now, and put them in here too.

Cheers.