ok so my grandmother has a 92 dakota with only 103,381 miles on it all original been garage kept never been smoked in at all still looks brand new off showroom floor she has had lots of parts replaces TPS, IAC, MAP, (Ect.) but yet it still has an issue of not wanting to level out the idle as long as the rpm's stay higher that 2000 it will run great but as soon as it begins to drop below this rpm it will begin surging up and down and dropping low enough it sounds like its bout to stall out does this constantly until it actually does end up stalling out but as soon as u pull it out of park no matter what gear selected it will begin to level at at normal idle 700-800 rpm and will not stall after getting it outta park or as long as u have the a/c on it wont surge or stall out but as soon as u put it back into park like when parking to get out of the truck it revs up and instantly stalls hot or cold but when starting back up and trying to pull it into gear or shifting between gears ya have to kinda keep your foot on the gas feathing it to keep it from stalling till its actually in gear. Check engine light is on and have checked it the only codes it is throwing is 22,51, first one is coolant temp outside of range. and the second is simply jus running lean. please i know that this is got to be a very simple fix we have thrown money at replacing sensors serveral different times sum1 plz help!!!!!!!!

 

Created a new thread for you instead of resurrecting a 7 year old thread.

 

Need to plug in with a scanner, and see what the PCM thinks coolant temp is. Next, I would check fuel pressure. Throttle body, or port fuel injection??