Thanks Vee
Thanks for the tip about piercing probe, set on order. Already tried the paperclip, not enough space.
I can get a new TPS for £260. / $340 .
If it is non adjustable can I just be swapped for a new item?
Is the calibration by mechanical means or is don with software through the ECU?
Last resort will be taking it to a local Jag specialist.
Next issue will be removing the 28 year old screws holding it to the throttle body, I had to drill out and tap the screws holding the Idle control valve.
I will post an update with any progress.
Regards Tig.

 

So….

The ECU and TPS are basically in a relationship.

From the factory, the TPS, at idle, is 0.60V. But over time, things get less precise and the TPS begins to creep. How far? Maybe 0.64V maybe a bit more, maybe a bit less. As things get less precise and the TPS moves off of the factory 0.60V at idle, the ECU learns with it, so everything stays cool….until it doesn’t. Which is where you are now.

If you replace that TPS, there’s a very very good chance that the TPS will show a different voltage at idle than what it is used to seeing, so you’ll continue to have RPM issues until the TPS is reset.

The TPS reset is almost inevitable. There’s no good way to avoid it. Jag dealer should charge you an hour of labor to perform this 5 minute reset.

The only other thing I want to mention is that occasionally I have a hiccup where the car wants to idle high, so while running, with the engine hot, I reach under, disconnect the TPS count to 10, and plug it back in. More often than not, the idle drops back down to normal.

Not always, but worth a shot.