V12 not idling and stalling

[craigjm]

My 6.0 isn't running right. All of a sudden it's started stalling rather than idling although when it's on the move it runs fine Along the motorway at whatever speed you want. What could cause that? Starting to annoy me now because been for a long drive today but as soon as you're off the motorway I've had to really anticipate islands etc so that I don't have to come to a complete stop to prevent it stalling.

Help please

[QuickQuack]

craigjm said:

My 6.0 isn't running right. All of a sudden it's started stalling rather than idling although when it's on the move it runs fine Along the motorway at whatever speed you want. What could cause that? Starting to annoy me now because been for a long drive today but as soon as you're off the motorway I've had to really anticipate islands etc so that I don't have to come to a complete stop to prevent it stalling.

Help please

Could it be a knackered idle stepper motor? Shouldn't be an expensive part as far as I know.

[craigjm]

That is a possibility will look into it

[johnxjsc1985]

been a while but I seem to remember my 6.0l had a dodgy or sticking idle control valve

[craigjm]

I think it probably is that. Going in to be sorted end of the week

[tortop45]

Check out the cats on the exhausts could be blocked up.....

[craigjm]

tortop45 said:

Check out the cats on the exhausts could be blocked up.....

AFAIK it doesn't have any cats on it. It's the early XJRS 6.0 engine fitted into a 70s XJC with a stainless steel exhaust

[johnxjsc1985]

craigjm said:

AFAIK it doesn't have any cats on it. It's the early XJRS 6.0 engine fitted into a 70s XJC with a stainless steel exhaust

I had the 6.0l XJS and it had similar problem through lack of use I seem to remember the valve in question was near the bulkhead on the passenger side but like I said its been a while

[craigjm]

johnxjsc1985 said:

craigjm said:

AFAIK it doesn't have any cats on it. It's the early XJRS 6.0 engine fitted into a 70s XJC with a stainless steel exhaust

I had the 6.0l XJS and it had similar problem through lack of use I seem to remember the valve in question was near the bulkhead on the passenger side but like I said its been a while

You're right that's where it is. My car is new to me but has done minimal mileage in the past two years so could well be that. Getting it looked at weekend

[rougemont]

The mechanical side of the tick over is controlled by throttle butterfly gaps(.002" from memory) and auxiliary air valve, its very unlikely to be the air valve, normally when they stick it increases idle speed as opposed to the opposite. So check throttle bushes , these can break up, clean up throttle bodies and check gaps. Check for any air leaks around the inlet manifolds and associated pipe work . When did it last have a plug and lead change? Give it an Italian tune up and check both tail pipes for an even beat.
If this does not cure it need to know what engine management system you are running, if the engine is from a pre facelift xjr-s 6.0 ( jaguar not twr) then it may well still be running the original zytek engine management system which will require a specialist, so I would try to rule out basic service items first. good luck

[craigjm]

It's going back to XJ restorations to have a look at it. The Zytek stuff has long gone and it's running on a modified ECU from AJ6 engineering as it has many of their other mods too. Had new plugs leads rotor coil etc just before Christmas. I'm sure they will sort it out. Thanks for all the suggestions

[tortop45]

Give it an Italian tune up and check both tail pipes for an even beat.
Thats a great place to start,least you can work out which side might be playing up.the air valve on the near side of the engine is to assist cold starting and when engine is hot is for ajusting the idling don,t ajust the idling speed at the butterfly,s on the intake manifolds.when was the last time you changed the fuel filters......

[craigjm]

Definitely more coming out of the drivers side exhaust at idle

[craigjm]

RAC came out and had a look at it and he altered the throttle body to stop it stalling but recommended I take it into the garage. Emptying the boot today to get it ready to go in I happened to notice that the vacuum pipe had come off the ECU. Refitted it and it started first time. It now surges in park idling at about 1500 and dropping to 1000 in drive. I think I will get the RAC to come out in the morning and reverse their tinkering with the throttle body and we might, just might have solved the problem.

[melhookv12]

You say it has a XJRS 6.0 litre engine. Ecu is in the boot. Which ,anagment system are u using? It should be zytec.

Anyway, ur idle speed is too high. Hence the surging. The idle valve is on the left hand rear water rail. These seize and effect idle. Get rac to undo their bodge. Then get a jag man to look at it !

[craigjm]

melhookv12 said:

You say it has a XJRS 6.0 litre engine. Ecu is in the boot. Which ,anagment system are u using? It should be zytec.

Anyway, ur idle speed is too high. Hence the surging. The idle valve is on the left hand rear water rail. These seize and effect idle. Get rac to undo their bodge. Then get a jag man to look at it !

As i said above the Zytek stuff has long gone. It has a AJ6 engineering modified Lucas ECU on it along with a number of other modifications from them.

The RAC will be undoing their bodge today