i have a 95 civic 1.5 DX and the car is idling up and down,any solutions on what can be causing this?I heard this is a common problem on honda's.any suggestions will be appreciated.

 

You most likely either have a bad IACV (Idle Air Control Valve), or you may just need to adjust it. This can be done w/ a flathead screwdriver. Just leave your car running and as you adjust it, listen to your car's idle. Keep checking your rpm's at idle speed, and it should be between 700-850. Check that, and come back....

 

My Si was doing the same thing. Sound was very consistent and even. Like you're reving the engine, but you're not. I had the wrong ECU in the car, a PO6 instead of a P28. Once I go the right one, the problem went away, but came back a week later. I guess the way to go is to change the O2 sensor(s). Old. Too old. To add insult to injury, went to chagne the header gasket, and the stock header was cracked down the middle like an earthquake fault. I'm picking up a DC sport header tomorrow, and will change the O2 sensor. Not sure if you should change both if you change 1. I'm hoping the problem will stop.

Hope this helps. Thanks for bringing this up.

Hmmmm.....One sensor on the header and one after the CAT?

 

BTW.. cleaned my IACV. Blasted it with carb cleaner. It was VERY clogged. Looked new when I was done spraying it.

 

excellent idea !!! check IM, and adjust manually if you have to. make sure everything in and around the IM (ie: intake, IM, valves, etc...) are all clean as a whistle and go from there.

 

Yea, i forgot you can also try cleaning it, as it could just be clogged.

 

i will try cleaning it tomorrow,thanks

 

You may also have a vaccum leak somewhere.

 

Most likely. Tell us more about it. Does is do it when cold and warm, or just after the engine warms up? Consistent from 1000-1500 RPM or all over the place?

 

If your idling fluctuates up and down during cold start and goes away after operating temp is met, your Fast Idle Thermal Valve has backed out.

If your idling fluctuates up and down during operating temp, then it is most likely the IACV.