I have disabled the moving part of the AAV and now it is just an idle speed adjuster. For cold starts I have incorporated a Jaguar part as used on the 3.6 inline 6 cars. This is the part:
https://www.jaguarclassicparts.com/u...alve-3-6-litre
Number 8 in the illustration. It is a solenoid valve just activated by an on or off switch, which I have cabin mounted. The intake/outflow pipe is about 13mm diameter.
What I did was to buy a T piece of hose 1 inch ID with a 1/2 inch ID leg of the T, and incorporate it in place of the LHS balance pipe manifold to balance pipe hose, and place the solenoid valve on the leg of the T, using a dinky little filter on the intake. Works fine, simple and manually controlled, gives about 900 RPM in cold weather starts.

 

This is also documented in the "XJ6 Series III / XJ-S 1987 1988 Electrical Guide" (how relevant that would be to an earlier car I don't know), except for the exact numbers concerning temperature vs. resistance and voltage, which is in the "XJ-S Engine Performance" document. Per the document, it applies to "all H.E. and later models with P type fuel injection".

Both are available for download somewhere on this site.

Thanks,

John

 

 

Talks only the the ECU

Yes, the sender/sensor for the gauge is on the RH side, single wire, green as I recall

Cheers
DD

 

So... If the CTS is faulty will she chew fuel thinking it is cold all the time?

My exhaust looks fine, but boy does she chew the fuel. I reckon I'm getting about 220 - 250 miles per tank!

12 or 13 miles per gallon and I live rural so most of my speed sits at 60-70 MPH

 

I have done similartto Greg, but deleted the balance pipe etc all together.

The write up is 12mb, and way too big to attach, and my laptop is having a female moment and will not allow me to save it as a PDF. so if you want that PM me your direct email and I can do the deed.

I will be OFF the air from AM tomorrow, until Sept 24, so get in quick if you want anything.

Economy, oh boy, many items at play here.

Ignition timing (NOT factory settings)
Mechanical advance (inside the distributor),
CTS, as mention,
ATS, not mentioned yet,
Oil viscosity,
Fuel quality,
Your Right boot angle.
Engine Temp.
Spark plug condition
Trans fluid integrity
Exhaust flow, its OLD now, maybe restricted a tad.
Etc, etc, etc.

Mine averaged 11.2L/100kms on Interstate runs, and around 20+ in the Burbs.
,

 

 

Thanks JigJag

Ok, so are you saying that by closed circuiting the CTS and the ATS (Air temp sender on the LH aircleaner?) then the ECU will cease to enrich the fuel?

Are you also saying they are variable sensors or are the CTS or the ATS normally open or closed or variable when cold?

Cheers

 

Yes, and variable.

The CTS is a PRIME fueling signal, Example, running V12, unplug teh CTS< Dead V12, its taht simple.

The ATS is a trimmer, and has no huge affect.

Bridging the CTS will inform the ECU that engine is HOT, so lean off the fuel map in its brain to that spec. Mongrel to start Cold when bridged.

There is also another enrichment switch. Called a Vac Full Load Switch, and usually hanging around near the 5A intake ram. It has a vac line to the rear of the RH Inlet manifold, and either 1 wire, or 2 wires, depending on Jaguar stock on the day your beast came along.
It requires VAC to keep the internal contacts OPEN, and thus the ECU stays in closed loop. Vac drops, as you accelerate, and the contacts CLOSE, which effectively earths that ECU circuit, and the fuel is about 15% richer. This all works in conjunction with the TPS firing ALL 12 Injectors as you stand on the Gas, and the beast leaps forward rather quickly, WITHOUT coughing back. Much like the old school accelerator pump in a carby. SIMPLE really.

Synchronisation is paramount for all this to flow.

Read teh attached a few times.

 

Doug: So how do you rebuild one (AAV)?

 

The Great XJS Prophet (bows to the Southern Cross) is on holiday, but I am sure he will forgive this impertinence:
https://www.jaguarforums.com/forum/x...ebuild-119510/

Greg

 

There used to be rebuild kits available in Australia, but no more unfortunately. I gather the supply of replacement wax capsules dried up.

 

Well,

I received my new AAV and CTS last week and just finished the installation of both.

To my amazement there was no change and she fired up from cold the same horrible old way.

I cleaned up the existing AAV and trialed it in a cup of boiling water to see if it was jammed or not. Nope! The old AAV was perfect.

In hindsight I should have removed first and tested it, however I thought I would destroy the gasket and decided to just buy a whole new unit with new gasket and hose.

So.... annoyed as I was I sat there with my beer thinking and imagining what the hell was happening and what I had missed.

I decided to fire her up and remove the AAV idle adjustment bolt to see if it would pull a little more air and as soon as I pulled the bolt out the AAV suked a huge amount of air and the engine jumped up to about 2500 rpm!

This confused me somewhat and after another beer thought ok the air cleaner must have been pop riveted shut at the AAV port. Nope... Thats not it

Ok so another beer and decided to remove the small air hose running from the air cleaner body to the AAV in case it had a blockage which I thought would be impossible.

BUT... Some ******** before me had stuffed a rag up it!!!

Problem solved and engine is away laughing now and a good $400 wasted money for something I didn't need.

 

So if anybody needs a perfectly good second hand OEM AAV let me know as she works a treat.

Happy to sell for $200.00 USD if someone needs a spare or a new one.

Here are the working images of the second hand unit. The gasket looks like new so cant be too old)

 

Well done.

SIMPLE cars, as I always say, Only complicated by the "nut behind the wheel", and NOT necessarily YOU.

Well done again, and YES, the beer is ALWAYS the answer.

 

Well for the first time when cold the Ol' girl fires up with no foot throttle needed and idles beautifully straight off the cuff.

I have adjjsted the warm idle with the AAV bolt and good as gold.

I lot of work for a sabotaged air hose!

I am at a loss as to why there was a paper towel stuffed up the guts of the air hose connecting the air cleaner to the AAV body.

Any ideas why someone would do that?

 

To mask other issues.

I have had them with a rag actually AT the air cleaner end, simple find and fix.

Usual culprit is high idle that cannot be tamed, so plug the intake, and sell the car.

The list would be loooooong, and not worth the effort in my opinion.

There are mechanics, and then there are "mechanics" and sadly the V12 seems to gravitate to the latter.

 

 

My local Jag tech puts a cork in the air filter back plate hose opening. Then drills holes to get the wanted idle speed.

Rob