I have a 92 Honda Civic LX, Automatic,1.5 L. It has been having this idle problem for months now. I was also having a starting issue, but that seems to be fixed for now.The idle surges high and low when slowing down while driving.It will go up and down as I take my foot off the gas and when I press the brake, then when I come to a complete stop, it will also stop. If the car is in Park, it will surge up and down continuously. Let me tell you everything I've done, and see if you have any more ideas....I replaced the air filter, fuel filter,fuel pump, idle air control valve (twice), checked for vaccum leaks ( 2 or 3 times), Had the map sensor checked (mechanic says its working fine), and the main relay. The car has a new alternator and battery. I took the cables off the battery each time I installed a new part, to reset it.... Any ideas and help are appreciated. I've taken it to two mechanics who are scratching their heads. This car is driving me crazy! Thanks! -Julie

* I forgot to mention, my check engine light is on. It is throwing a "brake" code. I need new brakes on the back, so I attribute it to that, but maybe that isn't it?...*

 

do you have a/c? if you do is it blowing cold air?

 

Warm up engine. Let it idle in Park. Turn A/C off, all lights and other electrical options also off. Radiator fan should not be running (if it is, wait for it to cycle off) Unplug the wires on the IACV. Engine should slow down to almost stall but not stall, and stay steady at that speed. If it still goes fast, you have too much air going in some other route.

What is the code number? I didn't think there was a "brake" code.

 

also if your a/c isnt working the engine will surge when the A/C button is on, thats what happened with mine

 

Yes, I have AC. Yes, it's blowing cold. I will have to get back with you on the "code" waiting for the mechanic to call me back. I think it was 7? I will ask and repost. My odometer/speedometer doesn't work and sometimes "comes to life" every now and then. I figured it was the VSS. I have ordered it, still waiting for it. Not sure if it's related to my idle problem, but I thought I would throw that in there. Thanks for the replies. Any advice is appreciated.

 

Okay, so it turns out my fuel pump was going out and my vss sensor was bad. I replaced both and did a tune up (plugs,wires,cap,rotors) Now, the idle problem is fixed except in park or neutral. It idles fine in drive and reverse, but when I put it into park or neutral, it surges up and down.Any ideas?