Does anyone know the size of the restriction hole on the EGR valve where the vacuum hole connects
On a 1994 XJS 4.0 With US spec
The OEM has one most replacements do not

 

I just read your post and I was wondering what was the reason you were asking about the EGR valve restriction hole. Then I went to check for that in the shop manuals and, to my surprise, I could not find a single point where they mention any "EGR" valve whatsoever, to the point that I was beginning to wonder if my '94 4.0 L XJS really does have an EGR valve, but it must have one since you have an EGR valve in your '94. Is it possible that the shop manuals call it a different name rather than "EGR"? I checked under "Emission Control 4.0 Litre", "Engine Management 4.0 Litre", Fuel System 4.0 Litre and "Exhaust 4.0 Litre" and never a single mention of "EGR". Is it located under that shiny chrome cover on the exhaust side of the engine? Now I'm curious. Thanks for any info you may add.

 

Just Google EGR valve for a 1994 XJS 4.0

Exhaust Gas Recirculation
It's mounted on the top of the exhaust manifold
I replace my valve and Now have trouble at low speeds below 7/8 mph
The engine wants to lope or surge
I put a vacuum gage on the hose to the valve it's getting vacuum at low speed
Iam not sure if the ECU is causing this?
But no one will answer my question on This Forum
Or give hints on what to check
So I have disconnected the vacuum hose at the valve and plugged it.
That's my answer to the trouble. Runs great now Car has just over 54,000 miles

 

ohsix,
People on this forum are as eager and willing to dispense advise and help as anywhere else I've seen. Sometimes it might be helpful to be (a) patient and (b) a bit more descriptive about the car you are fixing and the issues you are dealing with. And sometimes you just need to remind folks by asking again. Don't give up!

 

V1rok sorry for the rant
I was surprised to receive a email about my problem. After 450+ views
Posted problem July 2016
My Vehicle is a1994 XJS 2+2 with a 4.0 it's a Automatic
I replaced the EGR valve after a code that the EGR said it overheated the EGR valve was bad
I replace with after market valve from a Jaguar parts outlet Dealer
I now has a surge at low speed below 5 mph
I have vacuum at the valve even at low speed.
Vehicle Doesn't display any fault codes
I did pass emissions and will get Antique plates in two years
Thank you for the advice

 

[QUOTE=ohsix;1678161]Just Google EGR valve for a 1994 XJS 4.0

/QUOTE]

In regards to my docs for this car not ever mentioning "EGR" anywhere, I wonder if the EGR valve did come with the 4.0L engine from its very beginnings to the American market because, although my page title says "Emission Control 4.0 Litre", the bottom of the page(s) says "March 91", which leaves a very narrow time segment between the start point of the 4.0 L engine and "March 91". I need an updated "XJS Service Manual".