2003 jag x-type 2.5 with 105k miles on it automatic
excuse my horrible punctuation

recently the car has started going into limp mode when decelerating so i pull over turn it off wait about 10 minutes turn it on again and its still in limp mode doing up to 3000rpm shifting from park to reverse makes a hard bump and from 1st to 2nd as well.so i wait some more till it gets right and i can drive home.

i turned off the car and the next day i opened the switch and heard 3 quick throttles along with a rattle sound they both stop when all the dash needles become stable.then i turn the switch off and there it is the rattle sound by it self again till all needles become stable.but now a constant humming comes from the dash and or the radio/ac part.it goes up in volume every 24 seconds for a second.

the engine light is always on and the battery light is on most of the time also the radio goes crazy it mutes and unmute it self randomly.

the car was under the sun for a good 2 weeks before all this started.it could be some melted cables but i don't know.i got the codes read and it came back with

p0121 throttle position sensor
p0430 catalyst efficiency low bank 2
p0442 evap system leak

please help me narrow down the problem.

 

urahara, from the sounds of things, your plug to the TPS has become damaged due to heat and the connector is not making great connection and it is causing the computer to loose indication from the TPS. It then goes into a safe mode to allow you to get to a safe location, but not to give the computer full control of the engine. I would check the TPS plug and then see what you have. It may also be possible that you have damaged wiring as this has been known to happen, but the damaged wiring will be to the side of the engine in the hole between the motor, strut tower, and the battery box.