hey guys, this is my first post here and its about my idling problem.

i have a 92 prelude si and after running it for a long time it begins to have terrible idling problems. it will jump up and down rapidly sometimes, like from 1000-2500 rpms rapidly, when the car comes to a stop. does anyone know what this could be. i read a post a long time ago of someone who had a similar problem and the solution was to take off a plate by the TB and there should be a plastic screw to tighten?? i looked for that plate but found no plactic screws inside.

please, any help is extreamly appriciated, especially since i just pulled into my parking spot, the RPMS jumped up while my foot was only a little bit oin the break and i ran inot the curb

James

 

i could possibily be your iac valve
did it start doing this out of knowwhere,
or did this happen gradually?

 

You should take another good look at it, you are in the right place. Take it apart carefully.
It's not really a screw like you're used to, you can tighten it and it should take away your problem. It's the white screw like thing you have to tighten.

If this is not the problem, maybe you have a vacuum leak.

Good luck.

 

yeah iac valve or vacuum leak. either one can cause rpms to bounce.

 

Start with the idle air control valve (iacv) (front of the intake manifold by the injectors. Has a plug and 2 coolant lines hookedup to it) and the fast idle thermo valve (fitv) (bottom side of the throttle body, has coolant lines) then move on to vacuum leakes and air in your coolant lines.

You can try taking the intake tube off and then covering a small hole with your finger on the inside bottom of the throttle body, if it smooths out then its the FITV, but if it doesnt that still doesnt completely exclude the FITV but its safe to move on and look around.

Do you get a check engine light?

 

no check engine light. and i do have a vacume line that is not connected to anything. i believe it was disconnected when the intake was installed, and there is a screw to stop the leak. could this cause it? also, im not sure if this helps any but the rpms only bounce when i am stopped, and only after i have floored/drove the car hard. if i dont take it up above 4-5000 RPMs in normal driving there is no bouncing. could u guys help me out by trying to describe where the iacv, fitv, and all other stuff is?

the only thing i looked at as a plate by the TB that i removed w/ 3 small philips head screws, and the plate has the work 'UP' on it. its a circular plate almost.

thanks for the help that u guys have already given me...

 

bump --- any more help?

 

Take off your intake from the throttle body... There should be somehting like 3 holes or so on the throttle bodies interior... They are circular.. A thumb can cover it.. Once you have it pulled apart and stick your finger up in there you will know what I mean.. Cover these holes one at a time.. Theres one on the bottom towards the firewall.. Cover it, if your car stops surging then we know exactly what it is.. This is a common prelude issue.. The FAST IDLE THERMOSTAT VALVE gets locked up after years of runnig coolant and gunk through it.. especially if your not runing honda fluid.. Its an $80 part from Honda.. Maybe that will help, otherwise your IAC just needs a good cleaning...

 

thanks for your help JTC, and sorry for being a noob but IAC means what exactly, and wher is it located?