I love the car even with the issues and the reason am determined to fix it by all means
Not so sure about what you are referring to, do mean as in the photo?
I donât also know the microswitch at the throttle you are referring to. Better to know it if you could me a photo sample of it.
That must be the correct sensor. If it sends the wrong signals, the engine wonât run well.
The microswitch doesnât exist on your engine, thatâs for non-american markets, but you do have lambda feedback, so Iâd like to ask others who do have Federal models if it could be that the car is in open loop when it runs well, and dies when it goes into closed loop -
can that be ruled out by disconnecting the lambda?
The silver filter is where the spare wheel is, in the right forward corner, right where your air bleed valve is.
And if your engine idles reasonably well your fuel injectors are working okay. Since fuel pressure likely also checked out, I wouldnât worry about the fuel anymore, it must be a metering problem unless there is not enough fuel delivered. Do you now have a decent amount of return flow into the selected tank? You can see the return flow with a flashlight below the filler neck, push open the little flap and have a look at the volume that flows back with the engine running.
Check the right front corner of the boot. It is probably there on all cars not some cars like I said.
Before I posted I looked on www.jag-lovers.org at the Series 3 XJ brochure in the fantastic âBrochuresâ section under the âInformationâ heading, halfway down the right side of the home page. The only engine photo is a small one with an alloy cannister just where the filter was on my XJ12 Jetronic car, so I assumed it was the same. But the silver thing looks like a coil on that thumbnail picture, so the filter will be in the boot. It will have a direction arrow on it. If you tae it out you may find grit if you empty it into a jag. Your mechanic probably changed it though if he was doing the changeover valve and pump.
Whatâs that lambda thing you have been mentioning, where is it located?
Your mechanic will know! Itâs for measuring exhaust O2 levels. Does the stumbling happen all the way through the warm up phase?
OK, this issue now happens when step on the gas paddle to accelerate the engine
But does it happen when you just started the engine, or only after five minutes, or only when it is at operating temperature? Or at all times?
Try narrowing down if it is related to a certain rpm or temperature.
Does it only happen when you push it in quickly, or also when you slowly bring the rpm up and depress the pedal?
Does it stumble when you put it into Drive?
Standard procedure 
The filter should be in that location on all FI cars. Thereâs tank filter socks as well, but I donât yet think fuel pressure has too much to do with it since the mechanic changed the pressure regulator and likely declared that fixed.
It happens all the time
The mechanic has just confirmed to me that the whole trouble with the car now is the fuel system.
An EFI fault should not really be solved by changing to carbs, Michael - mending the EFI should be sort of straight forward�
Frank
xj6 85 Sov Europe (UK/NZ)
**
How straight forward?
If he thinks he has it, thatâs very good news!
And we all know that the EFI can be somewhat elusive at times⌠but changing the entire car sure isnât quick or easy either, and also costs money (fuel pump, all the previous diagnoses wasted,âŚ)
Itâs a boring old L-Jetronic after all.
That must be the correct sensor. If it sends the wrong signals, the engine wonât run well.
Hi David,
Aside replacing that sensor, what other way can we check it works well and give the right signal?
The mechanic has already point to that.
Am not get quality of the sensor from the local market, the brand new one I bought locally exploded when fixed and engine was started.
I have also bought few used ones and they all send wrong signals.
Could it also be the sensor harness through to the ECU, if it happens to be this, how could that be solved?
I should have said âsystematicâ, Michael - starting from symptoms; what has actually been done so farâŚ
Frank
xj6 85 Sov Europe (UK/NZ)
**
So far, we have done/replaced as I have listed on the page/# 13/38 of this post. Link below
It can cause a lean stumble, which potentially includes dying when pushing the throttle, and potentially hard starts. Connect it to a Multimeter, put it in a pot of hot water, look for a smooth curve and compare values. Thatâs what I did.
Itâs purpose is mixture adjustment in relation to engine temperature.