chrisyd

Hello Guys

Once again im calling on the help of anybody with advance jag knowledge, well anybody that knows more about them than me as this is my first one. I have a 1991 XJS its not very happy, when it starts it will hunt from idle to 2000 rpm up and down continusly, i have no clue why ? seems the ecu is telling it to do this, im completly stuck so any suggestions would be really appreciated.

Thanks in advance

Chris

mikelmr

air leak after the throttle body somewhere ? inlet manifold gasket ?

Shark Man

A Vacuum leak would a first point of call to check for - with the masses of vaccum pipes a Pre-1992 car will have you'll be quite some time!

There is no idle control valve on the car - so the ecu does not control the engine speed (unlike post 1992 catalyst equipped cars).

micared

What engine does it have? If it's a 4 litre check the idle speed control valve, the throttle potentiometer, and, if the ecu is in the passenger side front footwell, check for water ingress around that area, front screen/ sunroof drain blocked/ door seal area, they all leak. Think it's the throttle pot that gets knocked sometimes when the oil filter gets changed, and throws a fit, if I'm remembering it wrong, someone'll be along to put me right. Not a well known fault if it's a 3.6 or a 12, although ecu is always a good starting point! Good luck.
Whereabouts are you?

chrisyd

thanks for the help guys

turns out to be a vacum leak right enough, the cold start air regulator was stuck, the unit connected to the cooling system. as it turns out i bought the car as non running project, got the engine running after some niggly problems, then i look at the exhaust and it appears my internal combustion engine is now a steam train, ahh !!!!!! left hand bank head is warped.

so the engine is coming out and in its place is going a reliable chevy 350 small block with easy to set up carb. incase your wondering, im out in florida for a while and these engines go cheap as chips with standard 350, few minor mods give me a nice 450 and a much more reliable car.

thanks for all your help

chris

Shark Man

Good idea...the last thing you want is to try and pull off the cylinder heads off these things! (btw if you do...keep the engine in the car...you need to hold it down to pull the heads off!).

Maybe an idea to dump the old th400 tranny while you there for a 4 speeder such as a 4L80

brickboy

At least it won't rust too badly in Florida

Jonathan Davies

Jag-lovers has a section for owners of Jags with lumps in:

http://forums.jag-lovers.org/index.p...xgLHCwDHiNE%3D

Lots of yanquis on there too!

chrisyd

sharkman

have you pulled of the v12 heads before ? i did try after stripping all the fuel inj equip/manifold and a million vac pipes, the head is stuck on, nothing i tried would take it off, thats when i gave up and decided to convert to something a lot less complex, just out of interest, how do you separate the head from the block ?

brickboy

Chrisyd -- on the six-cylinder Jags it used to be common to attach chains to the lifting points on the head, and hoist the front of the car up using the chains so the front wheels are just off the ground. After a day or two the head joint will separate.

Sounds like an urban myth but it's true ....

micared

Yeah, absolutely right!

J4CKO

iTrader: (1)

Hmm, my brother in law has a V12 E-type, its overheating, possibly because its on its original radiator (1974) doesnt get run that often and has always been topped up with tap water.

I am thinking he could be in for a big expense....

fatherpierre

My 91 XJ6 did exactly this.

It used to cut out too.

New Lambda sensor sorted it.