I've got a bit of a strange problem.

When my car is fully warmed up, it idles fine at about 700-800rpm. But when you start going past about 5mph and the car is in neutral, it won't idle below 1500rpm, unless the car is basically stopped.

What's the problem?

 

Bump,

No one has any suggestions??

 

Any check engine light on, vacuum leaks?

 

just throwing this out there...what about a speed sensor? Ya think that went bad? I've got a bad one that keeps throwing my SES light, but nothing physically changes that I notice. I'm gonna stop while I'm only a little behind, because I don't know anything about your problem lol

 

completely normal. It's programmed into the ECM to open the IAC valve when you'r moving. It's designed to help reduce HC emissions on decel and to reduce driveline shock if you were to release the clutch. All 3rd gens do it, it's just that it's only noticable on manual trans cars.

 

I understand that, but sometimes the car will surge between 800 and 1500 as if the IAC is opening and closing. Other times, the car just drops down to 800 with no problem. And then at other times, it just sticks at 1500 until I come to a complete stop.

I also had a problem today where the car's idle dropped to about 500 or so and ran rough, which is leading me to believe that my IAC is on it's way out.

Edit: there is also a dry vacuum line at the back on my intake plenum, but I don't think a tiny leak would cause something as random and severe as this. Either way I will be replacing the vacuum line.

 

its not suppose to drop below 1500 when your slowing down but when yer at a stop idle should be about 800. yer IAC could be or your vacuum might be leaking somewhere. check the vac lines then the IAC