ajusaf

on park and neutral the car accelerates to 2k rpm an back down and up but on drive its normal

Muddy9069

Mine was doing that...it was my Throttle angle sensor. Are you getting any codes??

ajusaf

Throttle angle sensor? where is that located? how much to replace? as far as codes i don't know how to retrieve them. i have a 90 dx

Muddy9069

Throttle angle sensor is on the back of the throttle body.. I dont think you can get one by itself...at least on my 86 you have to buy the whole throttle body... Dealer cost about $550. I just unpluged mine and reset my ECU and it's working ok till I can find another from a junkyard. With it unpluged you will idle a bit high...about 1100 instead of 800 but no more loping idle at least.

Your ECU is either under your passenger seat or under your passenger carpet. If it's under the seat and you have a code you will see red LED lights if you look from the front. under your carpet you have to count the blinks. just turn your key to the "ON" position and if you have a code you should see it.

ajusaf

cool never knew about the code how do you reset it? also unplugging the sensor will that make the car run bad or waste fuel?

augy

If your throttle cable is too tight that will also cause this. I swapped my engine and dealt with the jumping idle (from 500 to 1500) for about a week before my buddy just loosened the throttle cable and it went away.
Try loosening the cable first--it's fast and free