Engine will cut off for a half-second and then back on and run rough and keep doing this till I turn the engine off, this happens most often going up hills after the car has been driven for at least 2 hours and this will happen on a hot day when I am in traffic. Just noticed this also, when I first start the car I hear rumbling from behind me, it is not the antenna as the radio was off, lasts about a minute or 2 and then goes away.
Car does not have any codes and does not happen all the time, I can have it happen and turn off the engine and back on and car can drive the rest of the day up and down hills with no problems or it will keep happening about every 5 or 10 minutes, I was leaning towards a bad MAF or fuel pump, but from what I researched a bad MAF should always throw a code and never heard of a bad fuel pump lasting for 3 months (when problem started), so could the pump get weak when hot?
Should note that a flat highway going 80, I floored it to pass a car and the engine started cutting off and on and when I left off the gas and pressed it just enough to try to keep it at speed, the car started bucking like crazy.

So does the regulator send a signal to the computer when the fuel pressure gets to low, for the FP to send more fuel?
Trying to figure out if I have a fuel or electrical problem.

 

Sounds like the fuel pump to me. Check the fuel pressure first, if it's low, then replace the filter, then check again. If it's still low, it's the pump.

 

"So does the regulator send a signal to the computer when the fuel pressure gets too low, for the FP to send more fuel?"

The 01 XK does not have a Electrical Fuel Pressure Sensor.
03 was the first year for that.

 

Sounds like it cold also be a throttle body problem, or wiring/harness to the TB. Get some live data from an OBD II scanner, measure your fuel pressure while this occurs, look at your fuel trims too.

Have you changed your fuel filter...ever?

 

What goes wrong with the TB?
Just got the car 4 months ago, I have not replaced the filter or done the tranny fluid yet.

 

throttle body harnesses in the earlier cars are sensitive to moisture, and most often when stalling or hesitation at highway speeds are noticed, it usually points to a TB issue...the TPS, stuck plate, connector (pin to pin composition), and others.

 

I think it is heat related, I was think the MAF or some other electrical part else got heat soaked over time, as it only happens after the car has been driven a couple of hours and the problem starts sooner in hot weather than cold and the car acts up worse in hot weather.

 

+1

 

It was the pump, Thanks everyone!!

 

hot dog, good call oldmots and beav!