I've been going through the wiring on my XJS engine bay and spotted this Anti Stall Mod #51248758A. The wires lead from the passenger side front wheel side wiring harness to some kind of sensor located on the intake air filter box.
I'm not sure it's a sensor, may be a control mechanism similar to an IAC or something like that. The other side goes the intake side of the throttle body so I'm thinking that it acts like an alternate to the AAV and provides more idle control.

....Doug

 

Yup!

Later standardized and called the "EAV"- Extra Air Valve. Let's more air in for increased idle speed when a/c compressor is engaged

Cheers
DD

 

If I remember that was for the 45 secoNd delay that those cars were fitted with. The system was designed to light of the catlysts as soon as possible. I think the vac to the distributer was shut off so no vac advance, the air valve would open to incraese the idle. It would shut off after 45 seconds. The valve has nothing to do with the AC.

 

We're both correct. Here's the story from the Jaguar Tech Training "Focus" Guide:

Idle Speed Control

Initial Start-up

Each time the engine is started the starter relay activates the 45-second timer, which opens the supplementary air valve to increase bypass air flow for the first 45 seconds of operation.

Idle Stabilization

During air conditioner operation the supplementary air valve is opened via the idle relay to stabilize the idle speed. To prevent excessive idle speed with no engine load, the idle override relay is energized when neutral or park is selected. When energized, the idle override relay switches off the idle relay, thus closing the supplementary air valve.

VIN 104236-133460 Purge Modification and idle stabilization kit available.
VIN 133461-on Purge and idle stabilization modifications incorporated into production



Cheers
DD

 

Not sure where I came up with "EAV" when it's called a "Supplemental Air Valve". I've been calling it the "Extra Air Valve" for years !

Cheers
DD

 

Thanks for the replies. If the dealer did this, then it seems like a rather sloppy job I have to say. Looks like some sort of sealant ( glue ) was used on the passenger air box where the valve was installed. Doesn't seem like something Jaguar would do. I intend to fix that.

 

Supposed to be a rubber grommet. Last time I checked you can still order from Jaguar....in a 10-pack :-).

Something from the local hardware store oughta do the trick

Cheers
DD

 

I pulled this diagram from my AllDataDIY manual. It shows an extra air valve and supplemental. Shows two different locations. It looks like the Extra Air Valve is part of the Air Injection and the Supplemental Air Valve is part of the A/C circuit. Maybe I'm misreading it. I attached the diagram for your perusal. When I do my upgrade, I may be inclined to change this to some sort of IAC valve that can be controlled more accurately for idle.

 

We're getting crossed up in nomenclature

What is shown as "Extra Air Valve" in your diagram (which is the same as in my training guide) is commonly referred to as the "AAV"- Aux Air Valve--- the one at rear of the left cylinder head.

The solenoid operated device in the RH air filter housing is indeed the "Supplementary Air Valve". (Which earlier I was incorrectly calling the Extra Air Valve)

Cheers
DD

 

Ok, thanks for the info. I'll get my diagrams labeled properly to avoid confusion.

 

 

all i can say is Jaguar sure did some useless crap trying to get into the modern age , must have had cavemen to do engineering! (sorry my opinion).

thank the stars for Ford and India TATA to get nice cars today!

 

If by "EAV" you mean what is commonly called the "AAV"--Auxiliary Air Valve--- you can try cleaning it with carb cleaner or whatever. Might work, might not. Depends how badly stuck it is.

Cheers
DD

 

Not incorrect but a bit harsh

It's very much like what other manufacturers were doing in the 70s and early 80s. Lots of gadgets and gizmos strung together to keep car emissions compliant and/or make them run half-way decent. One device compensating for the results of an upstream device....and a downstream device compensating for the mid-stream device!

The difference is development....and, specifically, funding for it. By the early 80s most other manufacturers were moving on to better, more elegant solutions. Jaguar, which half the time couldn't rub two nickles together, so to speak, slogged along with clunkier technology. I suspect Jaguar engineers would've been tickled to death to get more R&D money.

Cheers
DD