The car starts fine when cold. After 10 mins or so she starts to run rough, this gets progressively worse until she will not tick over and then stalls and will not keep running. I have replaced the fuel pump, crankshaft sensor, throttle body and plugs yesterday but no improvement. I would say it feels like fuel as it is all or nothing, not like down on a cylinder or two. Any suggestions ? I really don't want to resort to the dealership. Thanks.

 

I would check the Coolant Temperature Sensor. I had a failed one and had bad idle and sputtering, stalling, not restarting which caused flooded cylinders..
If you have an OBD scanner try looking at the engine coolant temp, it should be somewhere between 175f to 195f. They are relatively cheap to replace if you need one.

Failing that it could be the Idle Air Control Valve, that will also cause stalling. There are some recent posts in the forum discussing these.
You could also be looking at a failed coil, which would be worth investigating.

All of the above are simple jobs you can do yourself. Dealer prices send a shiver down my spine.

 

Oxygen sensors? When was the last time you replaced the oxygen sensors?

It would be interesting to see the LTFT readings on your car. Do you have an OBD2 reader? They’re so cheap, but so darn valuable.

 

Had similar issue. Only after the engine heated up it would consistantly run rough for several miles and then stall out. After cooling for an hour it would start and run again for another few miles. New coils fixed it. Don't know why. After a couple weeks we put the original coils back in thinking maybe we just had a bad wiring connection, but the problem returned immediately. So it was definitely a coil issue for us.

Bobby

 

I endorse both BobbyDing and Vee's suggested diagnosis.

Oxy sensors cause all sorts of problems and should not be ignored. However the oxy sensor system in USA delivered cars is different to Australian delivered cars. (No pre catalyst sensors.) So I can't give you any firm guidance.
However I had a lot of stalling problems in one X300 particularly transitioning from high speed to idle. The engine would stall as you pulled up. Turned out to be oxy sensors

Ignition coils do decay and are affected by heat. I have had problems with hot coils however they have not been sufficient to cause stalling but pretty rough running.
I recently replaced all my ignition coils in one of my X300s and it has solved the rough running and breakdown under load problems
Bill Mac
MK1
MK2
S3 XJ6
X300 (x2)
15 previous Jags MK5 to X308

 

Picking up on your hunch that it is fuel related, have you checked the fuel pressure regulator? Easy to access and replace, and they do fail.

 

Thanks Nobeel, I don't have an odb scanner yet can you recommend one ? I will try the coolant sensor, they are cheap enough. I did change the plugs the other day and noticed the coils were the all black no-name variety. Would one or even two failing coils make it stall ?

 

Thanks for the reply's, on my way to pick up a coolant sensor, will try fuel regulator next. I will let you know how things work out.
Cheers Rusty.

 

can you recommend one ?

 

https://www.jaguarforums.com/forum/x...budget-249892/

 

I have been using the Veepeak obd2 reader with the free Car Scanner app on a iPhone.
it works pretty well for the price, but there many options out there

https://www.veepeak.com/product/obdcheck-ble/

 

iPhone or Android?

 

Yesterday I replaced the plugs for champion RC12YC which seemed to speed up the trouble kicking in so I changed back to the original NGKR6E which made things worse. Now it runs rough from cold. Aghhhhh !

My video does't seem to want to upload but here's a picture of the error I am now getting. This refers to throttle position sensor which I replaced last week for a supposedly good used one. I'm not sure where to go from here.

 

Are you able to check the throttle position according to the ecu? You should be seeing it at around 11% and progressing higher as you push down on the pedal.
if this is reacting properly, then the error could be a symptom of something else

 

Hi Nobeel, unfortunately no not until I buy a proper odb tester. I just replaced the old throttle position sensor which would only act up when warm. It is still running rough from cold so it cant be that. I'm not sure what to try now. I am going to order an odb unit hopefully I can get some results from it.

 

The new TPS would need to be reset for use with your ECU.

Champion RC12YC = NGK BKR5e
The NGKs with the 6 in the number equal the Champion RC9YC

Throttle position at idle should be at about 12.9%

Clearly you want to put back the original TPS...at least for now. That replacement might not be good. This is not a part you want to waste good money on used.

You haven't replaced the coolant sensor nor the oxygen sensor, right? Just the TPS? (The TPS is one of the sensors the car reads when cold, the oxygen sensor is not) The fact that the car seems to run ok when cold, means that it seems likely that its one of the sensors that isn't read until the car is warmed up. I'd still look at the oxygen sensors... if theyre original, the owe you nothing. They tend to go bad every 40-50,000 miles.

 

As you have worked out, you are going to need an OBD2 reader, but the good news is tat even the basic ones should be able to help you.
With the reader attached, go to "live data" and start the car. You will be able to see whether the throttle position reading progresses smoothly with pedal inputs, whether the coolant temperature reading makes sense, and what the O2 sensors are reading. You will be able to see whether your problem starts when she goes into closed loop for example.
You mention rough running after a plug change: could you have mixed up the connectors for coils 5 and 6? A very common mistake.

 

Thanks Vee, what do you mean about the TPS needs to be reset ? So now it runs erratically when cold also after the plug change over. I now reverted back to the NGK's but it still runs rough. So I did replace the coolant temp sensor for a new on but no difference. Hopefully an odb11 will arrive today so I should be able to give some data info shortly. I am also a bit confused about the plugs which am I supposed to be using ? Thanks.

 

Thanks Countyjag, I hopefully will get my reader today. I will post data soon. The wires from 5 & 6 are not mixed up the length for 5 will not reach 6.
Thanks for your input.

 

The TPS has a certain voltage reading when at rest, let's call it 0.60v. When fully open, it's at 5.0v. The ECU will learn, over time, that the throttle body no longer opens the way it used to, so now it knows that when the voltage reading at 0.62v means the car is at idle. When you come in and install a new TPS, that voltage reading could be different than the one you just pulled out. If that TPS is off by a fraction, then your throttle, when closed is at 0.59v. The ECU has to relearn the parameters of the new (to it) TPS. You can only do this using an OBD2 diagnostic machine specifically programmed for Jaguars....but there is another way.

You can take the voltage reading of the existing TPS, and adjust the new TPS to match that voltage. Regardless, I doubt it is the cause of your problem. A bad TPS either (a) shows up while you are accelerating and it hits a "dead spot" and lights up your check engine light as it shuts off your engine (!!!) or (b) would reveal itself even when the engine is cold, since it's one of the sensors the ECU uses at startup.

I still think the oxygen sensors need to be replaced.