That's the cruise control switch used on the AJ26 engine, the AJ27 was electronic. You are correct in that it goes to the vacuum solenoids in the fender well.

So what is it doing on a non cruise control car? Maybe someone replaced the original throttle body with the one you have now, and it won't work. I can't even find a wiring diagram for your version.

 

The cheapskate who bought my car new didn't specify cruise control (not that it would be much use here anyway), so here's where the pipe goes on a '98 non-cruise. Essentially, nowhere; it's pushed into the grommet that's conveniently nearby.

HTH,
Mike

 

completely different beasts aren't they? but so are the hose locations and such like so maybe i have the correct one on already but there is something amiss? thank you for looking though,much appreciated.

 

Looking earlier in the thread, Richie mentions P1226 which translates to 'Mechanical guard sensor range / performance'. I was intrigued by this fragment of technobabble and the apparent dearth of information, so I've done a little googling and come up with the following (my text), that relates to the early limited-authority throttle TBs.

First, bear in mind that in a normal situation, you press the throttle pedal, the electronics senses by how much, and instructs the stepper motor to move the butterfly to the appropriate position.

However, the throttle butterfly is also mechanically linked to the throttle pedal via the 'mechanical guard'. This allows the car to be driven in the event that the electronics let go and the stepper motor (which also drives the butterfly) becomes inoperative.

The vacuum servo on the TB is linked to the mechanical guard, and mimics the effect of pressing the throttle when the cruise control is operative. Where cruise isn't fitted, a vacuum supply isn't necessary, hence the feed pipe is just parked.

The P1226 fault is caused when the electronics senses a mismatch between the position of the throttle input (driven by the cable from the pedal) and the mechanical guard (the position of which is also monitored) driven by both the stepper and the throttle input. This is the part I couldn't get my head around at first, but there is a mechanical delay between the input and guard due to a pin and slot arrangement.
So, either a fault in the vacuum servo or a dud position sensor will throw the fault code. From what I can see, the latter is another part that isn't available separately

I hope this makes sense to those who haven't yet dozed off; the attached snippet will make things clearer. Note that the stepper motor isn't shown attached to the gears on the RHS

Finally, all credit is due to TheJagWrangler, from whose site this information came, contained in an article written by Mark Gallagher B.Eng. C.Eng MIEE (Electrical Engineering Department of Jaguar Cars Ltd.). The article explains the whole rationâle behind the engine management system, and most likely much better than I, pages 7 & 8 particularly:

http://www.thejagwrangler.com/uploads/8/0/2/8/8028029/jaguar_xk8_engine_management.pdf



My brain is aching. I think I need to go for a lie down.


Mike


P.S. - Richie, if you need any other pics. please shout

 

thats brilliant guys ,so we think new TB and job will be sorted?? would it need programming?

 

Richie, I'd backpedal a bit here before you start buying expensive new parts..

There could be more than one fault: the P1226 may be a red herring. One post in the thread suggested by jamdmyers says that replacing the TB didn't fix a p1226 code, nor was there a mention of stalling.

Could be the trans not letting go as suggested by mrplow58. I don't think a faulty brake switch will trigger the 'bulb fail rear' message on a non-cruise, and I believe the torque convertor locks up at low speed. If that's true I guess it needs to be told that you're stopping, and if it doesn't get the message?
I'm not a tech so I'll step back gracefully here and let the resident geniuses (genii?) chime in...

Good luck,
Mike