Hello gents
I had asked this question whilst discussing thermostat related issues and was advised to list this as a separate thread, and rightly so.
Whilst dealing with overheating issues and wrong thermostats, I saw 2 things sort of dangling in the engine bay and not connected to anything. First two photos below.
Whilst I got the answer to the small electric valve which allows the engine to rev up when the AC is engaged, and it is supposed to sit in a small hole at the back of the air filter housing next to it. I did check and the hole is there.
However, I still do not know where the lower tube is supposed to go to. Is there something missing there and is also supposed to connect from it to the back of the air filter housing, as I see 2 holes there, a small one for the AC valve and a larger one.
And what is the function of this tube?

On a separate note, whilst adjusting the slow running speed, I also saw a small micro switch that comes on when your foot is completely off the throttle (last photo below), and this makes the engine run a bit faster. Why is it so and would it happen to power the same valve when the AC is turned on to gain this extra rpm?

Learned a lot from you amazing gents and learning more still

Thanks




A closer look at the tube


Micro Switch to gain engine speed at Zero throttle

 

Does the tube wiggle? Can you see the other end wiggling at the back of the engine in the V? It looks like the air pump emissions system. The rest of the system can be removed fairly easily, but that tube is stuck there until someone pulls the engine. At least that's the case with my car and it looks the same.

 

The lower tube is part of the air injection system, as I mentioned in post 18 of this thread of yours:
https://www.jaguarforums.com/forum/x...mostat-283030/

It would origninally have been connected to an air pump, which may have been removed from your engine, as I cannot see it.
No idea about the micxroswitch!

 

The micro switch is for the Marelli ignition. As far as I know it is simply called an "Idle Switch". I can't remember if it is normally open or normally closed but, in any case, it should actuate the very instant the throttle is opened. The switch signals the Marelli ECU that the engine is at idle. The ECU in turn changes the timing to "idle strategy" (or some phrase like that....still on my first cuppa coffee)

Cheers
DD

 

Thank you for chipping in and apologies to you and the others who responded for my late reply, somewhat got taken off course by family events
Yes the tube does wiggle a bit at the end where it appears in the photo, feels sort of loose there but with very limited movement. Could well have been part of emission system as the car is with US specs and probably the previous owner removed it.
If as u say cannot remove this tube unless the engine is out, then it makes sense why it is still there.
But do I have to block it since it is not being used? Can it present any malfunction of the engine as is?

Regards

 

Hello again Greg.
OK I just had a look at your above mentioned post again to remember what you had explained, and I understand it much better now.
Hence my question now is can I just leave things as they are? And do I need to block the pipe referred to by me?
Thanks again for your continued support.
Cheers

 

Hi Doug and thanks for the explanation.
Yes this is exactly what I discovered that at idle situation, the switch is pushed by the adjustable bolt shown in my photo and the engine immediately goes a bit faster.
I will have to check if it is normally open or closed, for the benefit of adding info to this thread and will report back.

Thanks again for helping out.
Regards

 

Leave things as they are concerning that big pipe. But remove the 12 small pipes above the engine and block up the holes they leave in the inlet manifold as I mentioned in post 18 in the thread you referred to above

 

Thanks Greg, well noted and should be easy to do.
Do I expect to notice any change in performance or anything else?
Just trying to learn more.

Thx

 

No, nothing will change except that access to the engine V will be easier!