My 1998 Civic DX idles around 200-300RPM when sitting still. This seems a bit low, but is it normal? It runs nice and smooth and gets up to 40MPG. Its has an automatic transmission and a little over 169,400 miles on it.

 

im new here, but have you tried the seafoam? i think it helps with the idle and all, especially with 170k miles on it. maybe timing belt or somthing as well. idk, but thats what i would do. my 92 eg sits at about 500rpm but when its cold like 900rpm.

 

You don't need to change the timing belt unless it's never been changed or has been 7 years or 60K miles since the last one.

Your car most likely just needs a tune-up. Replace the plugs and wires. Inspect the cap and rotor for wear and carbon tracks - replace if you find these. Check the ignition timing with a timing gun. Also, clean the IAC valve.

If all of those don't bring the idle up, there's an idle air screw on the throttle body you can turn up a little tiny bit. This should be your last resort as you normally shouldn't need to mess with this.

 

I bought the car used about a year and a half ago, so I have no clue if/when the timing belt was changed. I had the car looked over before I bought it and about three or four times since and my mechanic hasn't said anything about the timing belt. The plugs look almost brand new, but I haven't looked at the other things you mentioned. What should the idle be?

 

Well, it almost stalled on me today. I haven't had the time to have it checked out. I was coming to a stop at a red light and I noticed the car was shaking quite a bit as I was slowing down. Then once I came to a complete stop, the car continued shaking and it was making a really slow "vroom, vroom, vroom" sound. I kept one foot on the brake and the other on the gas to keep it going because the idle was barely at 100RPM. I drove it to work and then back again and it was fine the rest of the day.