im new to forums so bear with me thanks. i have a idle problem with my car and i dont know what to do next. the car overheated on me and i changed the thermostat. when i started the car back up it raced really high about 2500 rpms then it slowly dropped to about 2000. then it started to jump up and down between 1500 and 2000 rpms just like someone is revving it up but noone is touching the gas. i brought it to the dealer they had it for 3 hours and cost me 300 dollars. they said they couldnot find the problem and needed the car for six more hours at 90 dollars an hour no thanks. someone told me to check the ecu so i pulled it out and sure enough there was a big burn spot on the circuit board. this has to be the problem i thought. so i got a new ecu and put it in and the car is still doing the same thing someone said to check the idle air control so i had it checked and it checked out fine but i got another one and tried that and the car is still doing the same thing i am at a loss. does anyone know what i can try next. i hate to junk the car its in fairly good shape. it has the 2.0 nonturbo engine. there is no check engine light on. thanks can anyone help

 

Change out the ECUs coolant temp sensor. You should have a sensor for the A/C and two for the coolant. One of the coolant sensors has one wire attached to it, that's the for the gauge, the other has two or three, I forget, but that's the one that needs to be changed. The ECU maybe seeing fluctuations in the coolant temp and adding gas then it may be taking it away (o2 sensor) and that can cause the surge too.
I only say this because you stated that you had an overheat not too long ago which may have "broken" that sensor. Otherwise, I'd be all over the idle surge controller or o2 sensor, etc., lol.

 

thanks for the reply. i forgot to mention i just changed out the coolant temp sensor and it made no difference what is the idle control is that located by the throttle could that be it thanks

 

just wanted to give an update. i was working on car today and there is a sensor by throttle body with one wire going to it when you unplug it the car races at about 2500 rpms but the idle doesnt jump up and down when it gets plugged back in the idle drops and then jumps constantly like before. also i noticed that there does not seem to be any vacuum at all. i pulled off a couple lines and didnt feel any suction. so i took lines off at throttle body there are 3 i could not feel any suction at all is this normal. it doesnt seem like it would be normal. is this why my idle is jumping. tomorrow im goint to try and blow out the vacuum lines and see if this makes a difference. also there is a selenoid on the firewall with 2 wires and two vacuum lines running to it that is making a clicking sound. could this be because of the vacuum any suggestions would be greatly appreciated

 

i cleaned out my vacuum lines and still the same i am down to changing either the idle speed switch or maybe the air flow senseor. if i unplug the air flow sensor the car idle really low but doesnt jump does anybody think this could be the problem thanks

 

I would maybe clean out your throttle body, see if that helps. Does it only do this when its cold?

 

thanks the car does it all the time warm or cold i will try cleaning out the throttle body and let everybody know thanks any more suggestions