I just acquired this car a week ago. It ran great for the long trip home (300+ miles), and then decided to start acting up a bit. When started cold or somewhat warm, the engine will run perfectly for a random period of time (10 seconds to 10 minutes), show a very brief check engine light, and then stall. It will restart immediately. Also, if I catch it early in the stall, I can manipulate the gas pedal and get it to recover (for the next random period of time). It finally produced a stored code that my OBD 2 reader could read - P0727 "Engine speed sensor circuit no signal". There was a second stored code P1775 "No DTC definition found".

Based on code P0727, I changed the crankshaft sensor on the front toothed pulley. The sensor was fairly crusty and old. The symptoms persist. If I can keep the engine running for around 20 minutes, the symptoms will nearly disappear, as if something is getting up to temperature. I swapped the relays for the fuel pump and high beams in order to see if it was a failing pump relay. No change.

I rummaged through a number of threads in the forum on similar issues, and didn't see one that had my particular set of symptoms. In the past day, it has stalled about 30 times, and has not produced a code that my reader can spot. Before I start throwing parts at this problem, I thought that I should check in with you all to see if you have any thoughts or guidance on "the next steps".

 

Do you have an EGR Valve?

 

Yes, EGR valve is among the possible suspects, but I am not sure if US models have EGR.

Apart from the CPS, another common cause of intermittent stalling is low transmission fluid, as the sensor fails to send proper signal to the ECU to match engine speed; here is a generic explanation of fault code P0727 that sheds lights on all possible causes. If topping up the fluid level does not fix it, move on to another. Other possibilities are too many, but a no-harm, low cost approach would be to start with fuel/injector cleaner and a new fuel filter.

There is a more comprehensive engine management questionnaire designed by Jaguar to obtain as much information as possible from clients about all concurrent or preceding symptoms associated with engine stalling to help the mechanic with accurate diagnosis, as even factory diagnostic tools may not be able to instantly tell what the real culprit is.

 

If you haven't cleaned the throttle body, egr and idle air control valve and made sure there are no intake air leaks in the hoses and boots you should.

Some say you need to reset the throttle position sensor but I carefully avoided mine and only cleaned the throat and butterfly and passages in the TB. Pulled and cleaned the EGR and IAC.

My idle improved vastly after doing so. Of course I have also done plugs and swapped in some better used coils.

 

With the specific P0727 code pointing to the crankshaft position sensor after a sensor change I would look at the connector at both the sensor ( slight tug on the wires ) and the ECU ( water gets in the connector ) . Make sure the ECU has a good case ground as well as the 6 other ground points in the engine bay .

The specific sockets you are looking for on the ECU connector are :

Black 19 , fuel pump relay control ground

Black 23 and 25 , CKPS sensor

Look for both tabs in the sockets to be pinching the blade pins on the ECU side as mine were missing the pinch .

There is also the possibility that you received a bad CKPS out of stock so the easiest try would be to try another one from a different source knowing beforehand that you can return it . The fundamental reading on the sensor is 1300 ohms resistance , the functional reading is a hard for the common person to measure .

The CKPS beside the engine timing component also tells the ECU to command the fuel pumps on by providing a ground to the fuel pump relays control half .

As the CKPS circuit fails not all aspects of the items it is connected to will fail at once .

One way to eliminate the fuel pump control is to just hotwire the fuel pump power wire . This will allow you to focus on the other aspects if you do not get a change of behavior . This fuel pump control circuit on Lady P. was modified by the previous owner to get around a fault and worked fine until the repair craftmanship failed over years . If you had the SC version of the engine it has 2 fuel pumps but the second one will not turn on until the ECU sees a certain RPM by again the CKPS

Editing

 

[QUOTE] Apart from the CPS, another common cause of intermittent stalling is low transmission fluid, as the sensor fails to send proper signal to the ECU to match engine speed; here is a generic explanation of fault code P0727 that sheds lights on all possible causes. If topping up the fluid level does not fix it, move on to another. Other possibilities are too many, but a no-harm, low cost approach would be to start with fuel/injector cleaner and a new fuel filter.[UNQUOTE]

I read the explanation of error code P0727, and realized that I had interpreted the code to be dealing with the engine crankshaft sensor, while the code actually concerns itself with the transmission. As an aside to my initial post, I am getting an occasional transmission warning light while having the engine stalling episodes (although not every time). Since I have no service records for this car, I think that I will change the transmission fluid and filter, and have a look at the connections to the speed sensor in the transmission. I hadn't "connected the dots" between that code and the transmission warning light. A further thought on this ... the stalling episodes seem to be most prevalent during cold and warm operation, and don't happen often when the car is thoroughly warmed up. Perhaps the transmission fluid is expanding enough when hot to avoid triggering the sensor? Hmmm. As others have suggested, I should wander through the various service items as well, and get this car as "up-to-date" as I can, from the perspective of routine maintenance.

 

The transmission electrical connector on the left side gets corroded and can be cleaned without jacking the car as this causes engine stalling problems and it wouldn't hurt the keep this item ahead of a issue now if not later . The AJ16 engine and ZF4HP24 transmissions are very solid on the X300 but look and protect the connector as a low investment in effort