I have a 97 civic lx sedan, 5 spd. all stock. Now the problem is that when I turn on the car the RPMs jump to over 2000, or sometimes it'll go higher almost to 3000, now I know the car has to warm up but its way to high, then when I start driving the car and roll to a light the RPMs still stay high untill the car comes to a stop, then some how the RPMs go down to 1000, or 1500, or just at 2000 again. Now the RPMs dont go down when I let go of the gas when rolling to a light, they go down when the car stops rolling!?

Now I tried adjusting the throtle body/choke, I thought the RPMS were set too high but it didnt realy do anything, I even sprayed wd-40 on the spring on the choke thinking maybe when I let go of the gas the springs was dry and wasnt pulling back and just stayed open, I know this doesnt make sense, but can any one help me!?


Also someone even said it might be my termastate is bad, and the engine keeps staying cold keeping the RPMS up to keep the engine hot, which kinda makes sense because after drving for over an hour and stoping at a light the RPMs act normal, but that doesnt explain why when I'm rolling to a light the RPMS stay high untill the car comes to a stop!?

 

Sounds like a vacumm leak...check all of your vacumm lines. An easy way to find it is to take wd and spray it where air could leak and if your idle fluctuates then its a vacumm leak...I doubt its your thermo...specially considering how hot its been lately....

 

+1 on the vac leak. That would cause an erratic idle. Just run through and make sure all hoses are secure and are not cracked...I am wondering if it may have to do with the brake booster considering when your holding the brake at a light it seems to idle fine.

 

thanks for the help I'll check all the vacum lines, and if any one else has any clues on what it could be thanks.