Hi everyone, John here.

I know this has probably been discussed at length but I'm completely stuck.
Ive got a 1996 long wheel base X300 4 litre and it's developed a fault.
Basically it runs fine til it gets hot then loses all power and splutters and backfires when I give it any accelerator.
I believe this may be caused by the engine coolant temperature sensor? I've tried swapping it out with one from a breakers yard but still no change. Could it be the Crank position sensor instead? Or maybe the camshaft sensor?
Also, going back to the ECTS, does that inform the temperature gauge on the dash? That has also stopped working. Is the dash gauge on a separate sender? In other words does the ECTS only inform the engine systems?

 

I always botch this one up. I believe it’s the camshaft sensor that’s gone bad on you. If you do a search on camshaft sensor, you should find enough posts that tell a similar story to yours.

i believe the crankshaft sensor is only needed to start the car.

 

Dash gauge is a separate sender. Both are on the thermostat housing, gauge is a single wire, ECU sender is 2 wires. As a thought, is the coolant up to the proper level?

 

Sorry VEE, yes you have botched it up.
The Cam position sensor is not required once the engine is up & running.
See attachment.

John Herbert

 

Change the crankshaft position sensor.

 

Hi John,

Welcome to the Jaguar Forums! It's great to have you with us.

With your symptoms, I wonder if the electrical connections to the ECTS and Temperature Sender (or "transmitter") could be damaged, disconnected or contaminated with coolant? They sit on top of the thermostat housing on the front of the engine, so they are easy to inspect.

The single-wire temperature sender's ground path is through the thermostat housing-engine-engine ground strap. Coolant or oil on the threads of the sender body can interrupt the ground. Coolant or oil contamination of the electrical connection can also cause the instrument cluster temperature gauge to be inoperative. Also, it is not uncommon for the insulation on the wires to harden and crack and for the wire conductors to even break.

The two-wire ECTS has its own ground path via the wiring harness, but those wires are also subject to head/age damage and contamination from coolant or oil, which can add considerable resistance to the sensor signal. The ECM interprets this high resistance as the engine coolant being very cold, so the ECM continues to apply cold-start fuel enrichment even after the engine has reached full operating temperature. This leads to rich running, stalling, and poor fuel economy. The situation is especially bad if your coolant thermostat is also stuck open (not uncommon).

Regarding the crankshaft position sensor (CKPS), they are known for failing at the most inconvenient moment, and their failure modes can cause weird engine behavior. It's a great idea to replace the CKPS preemptively and put your old one in the trunk as an emergency spare. Consider adding XJRengineer's timing advance bracket while you're at it.

Cheers,

Don

 

Did you check for codes?