Jaguar xj6 1995 starting & go for 15 mins

I recieved a 94 xj6 4.0 for free because it would run for a few minutes then shut down. it would start a while after but shut down again. the problem is using 10-w40 oil sends a low pressure signal to the computer when the motor gets to operating temp. , which shuts down the motor. the fix, use 5-w30 oil car is running great with out ever shuting off again. 8.5 quarts of fully synthetic mobil 1 the owner before me replaced oil pumps , electrical, fuel pumps.ect. n his mechanic still could not fix it. its our little secret

I have a 1995 xj6, the motor turns over but wont start, this happened once before and the repair place said they have to change oil and bore some valve out, something like a PCV valve because it was clogged and the motor wasnt getting the right amount of air. I hope u understand this. i checked my oil and it was low. any idea what they are talking about.

Have you ever had the filter replaced, if not then i would suggest that you do. Check it then, if it still does the same, remove the fuel filler cap and listen for a vacuum release sound, if thats the case, then maybe the tank breather is blocked. Are there any faults recorded on the on board computer ? is the check engine lamp on ?

Does check engine light or wrench light come on? If yes, get free computer scan from Autozone or other parts store that offers free scan. Sounds like a sensor is failing