V12 erratic / hunting... up and down

my 93 model engine has started idling rough / hunting … I thought podssibly the fuel filter was restrictes , so I changed it out… still about the same it will idle for a bit then when you touch the throttle it seems to get erratic ? this is not a high mileage engine so I do not think the throttle spindles are worn…

What about throttle spindle bushings?

This is just a guess because I have never experienced exactly what you described in either of our 1990 Jaguar V12s, but what about a failing Throttle Position Sensor?
I did have that hunting up and down after cold start due to a failed Auxiliary Air Valve (AAV). But that stabilized after a few minutes when the engine warmed up. A replacement AAV fixed that.


I hope that you are reading Greg’s posts about his Throttle Position Sensor (TPS) issues. It is possible that you are having a similar problem.


Hi Paul,
what I found was a somewhat seeminglt loose female spade connector going to the ignition box on top of the V… crimped it somewhat and seems muchooo better… My friend will now race the car because of my being unloved by big bro from pestpoint…he should be able to take at least one title, perhaps 2…Best Wishes… Art…

I am glad that you found the source of your problem. For something as important as the ignition amplifier wiring I would solder connectors rather than crimp them, but that’s just the way I do things.

BTW, I have no idea what the rest of your post means, but good luck with the race anyway.


are you in jcna …?

I’m amazed at how many such important connectors on this engine are simple wire spade connectors, such as ign amp to ECU, and all the ignition coil connectors.

I have no problem with simple spade connectors as long as they’re plated. Bare brass is ungood.

Hey Kirby, I like your word " ungood ", since I am barred for “life” from being a member of jcna, I have recently bought a Vantage V8… I still love all my Jags however…:roll_eyes::roll_eyes::roll_eyes::roll_eyes::roll_eyes::roll_eyes:

Ok I am curious, why are you banned from jcna? if you don’t mind me asking?

I was a member for 27 years…several of us were being pushed arou nd by this guy…one of my friends referred to him as King George…our greatest Jag Journal Editor " Mike Cook " was pushed out of his position after being with Leyland and Jaguar for most his life… he passed away last year, I believe he could not take the rejection… The dude in question is x westpoint and does not take criticism well… my friend from ( Seattle President for many years ) Steve Christensen wrote letters to local director barb grayson regarding geos behaviour… nothing done… most the other directors dare not speak out so I hear…fearing their doom from jcna… another conspirator is an old spinster fromm the bc club… not sure if this has turned into an old boys club or and old girls club… neither is acceptable in my / our minds… see what happens this weekend at POrtland ABFM… I shall be racing in the abfm slaloms, my friend in jcna as he is now a mwmbwer of the Ottowa club…
Best Wishes…

38 times National Champion Driver, many times fastest man in North American JCNA Slalom Competition… and more… told by htis guy " Art I am very good at getting rid of people " he certainly is.,…LOL, OMG one of the charges against me was at our events we were having 'Too many fun runs :" in the rules it states " fun runs are permitted after the slalom event timed runs have finished, and it is permitted by the " Slalom Steward "…LOL… I was the slalom steward… I guess I / we were having too much fun… himself not so much… now as administrato he gets a monthly salary to suppliment his westpoint pension…lives in south carolina… I am in Canada… long ways away.Mike Cook was one of the most knowledgeable Jaguar people in the world , esp in North American dealings… a friend we all miss… I have his book signed by hi “jaguars in America.”… signed to my son and I … To Art and Chase, Fast times and Fun… Mike Cook…

Thats a shame, it sounds like “King George” is /was on a bit of a power trip. Probably not used to people not being required to follow his every wishes like in the military.

Was he military? Or Westpoint Pepperill?

good point, I just assumed he was.

Either way, sounds like he was/is possibly a jerk.

I was military. My dad and brother also. And a multitude of friends.

Just didn’t want to assume too much from him being former Westpoint. But I know there are academy graduates that fit that mold.