WE have a 1996 XJ6 that has a continuing problem despite replacement of all 4 oxygen sensors, crankshaft position sensors, egr valve, both thermostat sensors, fuel pump, fuel filter, fuel pressure regulator, cleaned throttle body. After running for about 45 minutes the car intermittently loses power and sometimes stalls. The temperature gauge is is half way between cold and normal, despite running for 45 minutes when these episodes occurred.

Any help would be appreciated. We live in Palm Spring CA and any mechanic referrals would also be appreciated.

 

The fuel pump relay can be jumped on the fwd most socket to the aft most socket and this will bypass the fuel enable circuit and directly power the pump

The pump will run at all times with your key in your pocket so plan accordingly

use a blade type connector on the jumper and not just jamming a wire into the sockets

by removing the relay you bypass the relay contact points inside that can be burnt or the relay contacts floating

Look at the connector on the fuel pump itself for burnt sockets , this is a sign the fuel pump is giving out

The relay can be swapped

the circuit depends on the CKPS sensor which you changed but ........

The relay is powered by a fuse # 10 in the right heelboard fuse box and a controlled ground ( enable ) from the engine ECU closes the fuel pump relay

This fuse relies on the king relay in the corner of the fuse box to close and can be swapped with the one in the left engine bay fuse box because in reality it only controls the horn

The relay is at point 7 circle double hash in the pic below

The temp sensor for closed loop ECU regulation is the 2 wire sensor

Sorry to say the pump can be bad even though new

In changing the pump it is recommended to change the relay also along with pump connector inspection

 

That's a good list of replacement/maintenance items done. Spark plugs are not on the list. They could cause stalling if they are too old, out of spec or a brand other than Champion 71, RC12YC. Replace now if unsure.

The temp needle on the dash should be pointing up at Normal. The actual temp can be seen if you have a scan tool. Most likely the thermostat is failing by staying open, preventing the coolant temp from reaching the correct operating temp of about 190F. This causes the engine management to constantly overfuel the engine as it attempts to compensate for cold operation. A similar problem can be caused by the coolant temp sensor reading too low, but you have replaced that already. Also possible is a newly installed thermostat that is rated cooler than 190F.

 

Have you changed your thermostat? It's not on the list, only the sensors are. Your thermostat seems to have failed open. Fix that and perhaps the issue is solved, if not:

Coils and spark plugs are still a possibility.

TPS is another common culprit.

Lastly, there could be a vacuum leak. I had a leak at my intake manifold gasket that seemed to be very difficult to find. It cause a dip in the RPMs at stop lights every 32 seconds....your result may vary. With enough accessories on, AC, headlights, etc, it was enough to stall my engine at times.

 

Thanks for the advice. On my way to auto parts store now. What does TPS stand for?

 

TPS is throttle position sensor and not recommended to remove or adjust until you have a understanding of it

it is underneath the throttle body and there is a connector lock clip to secure the connector in place , mine was loose

There is a meter test of the TPS