3.6 manual cutting out at low revs once warmed up

[ptjs1]

Simon,

The Potentiometer on a 3.6 is EAC7341. DBC 2889 is for an AJ6 4.0 facelift car.

I know I keep saying it, but always check the Jaguar parts website first before you buy a part from Barratt's or Manners. It's the only way you'll guarantee that you've got the right part number.

Good luck finding one

Paul

[SimonR]

Thanks Paul, yes, I agree about looking the correct part number up on the Jag website. Try as I might, I couldn't find this one, probably just a failure on my account... Thanks for confirming the correct part number - that makes my job a lot easier.

I had a quick Google and it turns out that the actual potentiometer part is a different Lucas part number to the early V12 item (the 3.6 one is 73297a, early V12 is 73348a) so one of those with the correct plug fitted is unlikely to work.

I did, however, find a new item listed on the David Manners website:

https://www.jagspares.co.uk/product/thr ... eac7341%23

If only I'd realised that I was searching for a "THRTLE POTENTIOMETE XJ40 3.6" Weirdly, that part number doesn't list anything on the SNG website with the XJS filter applied either. I think there's something odd about how it's classified as SNG and Manners both think it's an XJ40 part...

[ptjs1]

Simon,

The Manners part seems to be out of stock. But SNG seem to have an OEM in stock. You just have to nerd around a bit in the XJS section to find it!

https://www.sngbarratt.com/English/#/uk ... 5B20734%5D

Cheers

Paul

[PaulGover]

This is almost certainly an irrelevant digression, being from a V12 viewpoint, but something might be useful ...
The throttle pot on my 1991 facelift went. Either they were NLA or wildly overpriced, so I ended up buying a generic throttle pot. Lots of injection systems use them, so there is a wide supply from electronic component suppliers like RS Components. Their special feature is they only turn through 90 degrees rather than the audio use potentiometer's 270 degrees. They are (or should be) low noise and jitter and wear resistent - one problem is the engine vibration causing jitter of the pickup, in turn leading to erosion of the resistive track.
The one I found was almost perfect, except it measured the wrong direction - make sure anything you get increases or decreases with a clockwise or anticlockwise rotation to match your old one. Otherwise you have to do what I did, mount it upside down, which means cobble up some new mount.

The sting in the tail, at least on the V12, is the purpose of said pot. You are probably thinking, as I did, that it tells the ECU how open the throttle is. Nope, it gets what it wants (and is the equivalent) from the air flow meter. (I expect more modern ECUs check to see if the airflow agrees with the throttle opening, and enter limp-home mode if they readings are implausible, but that's more modern than the XJS's ECU.)
What it's used for actually is producing a fast-changing voltage if you jump on the throttle pedal, so the ECU can enrich the mixture for max power. Think of it as the oil-filled damper in an SU carb. The ECU isn't interested in what the reading is, just in how fast it changes. I think it also inhibits fuelling on the overrun to prevent "popping-back", but it's a while ago so my memory may be faulty.