I'm having a problem with my 1996 X300. It has thrown codes of P0300(1/2) and P1314(2/2) consistently for the past week. I've changed plugs (proper champions). I've.changed coils. Switching them around with no change in engine performence. It idles with a slight skip, which you can feel when in gear. Driving it doesn't seem to have the same zip it had, by if you put your foot in it, it accelerates normally. Yet, at odd times it will pay down. Like an engine does when it runs out of gas. It goes flat, but a little bit of gas pedal and it comes right back. I'm leaning towards fuel pump on its way out. I've also cleaned the throttle body and mass air sensor and changed out the coolent temp sensor, and the fuel pressure regulater. I drove around with the gas cap loose to see if the tank was venting. It is. No change. No vacuum leaks that I can find. Any ideas or thoughts on this would be greatly appreciated. I've also searched this forum on the fuel pump conundrum.

 

potentially crank sensor or throttle position sensor related.

you could throw parts at it (crank sensor is cheap, easy) or be patient and measure fuel pressure at the rail and rule out the pump

 

Crank sensor changed. Could be tps. It did start acting up about 25 miles after cleaning throttle body. Which wasn't very dirty. I did use throttle body cleaner. Why would or how could the tps cause the engine to go flat and then come back?

 

" It goes flat, but a little bit of gas pedal and it comes right back "

The TPS is a variable resistor that is easy to test . On the middle wire of the connector put a meter on it and it will measure at idle around 0.60 volts dc with the engine not running but the key in the run position . If you very slowly rotate the butterfly the voltage will slowly and smoothly climb toward 5 volts

You should not see the voltage spike to zero

This TPS connector is under the throttle body so you can pik up the ( green / yellow ) wire as it passes over the fuel rail

See page 57 and page 56 connector PI 105 - 12

http://www.jagrepair.com/images/Auto.../jagxj1996.pdf

This loss of TPS will cause the ECU to reject it and and revert to a less then optimal set of data maps to run

once the TPS signal is seen again at a different throttle spot in a acceptable range The ECU will revert to normal operation

This takes adjustment time

The FPR will measure 43 PSI at idle and the attached vacuum line will bring it up to 46 psi on throttle up

Hard to measure finding the right fittings

You can swap the fuel pump relay for the Aux relay in the trunk on the same row , you can have burnt power contacts inside the relay

Check the fuel pump connector for burnt pins and sockets

Chevron fuel injector cleaner in the tank

 

Resolved. O2 sensor orientation. Lower rear sensors hooked up the wrong way. Switched the connectors and all is well in whoville again. Thanks for the help.