Higher than normal idle

[elspectro29]

Well, I've been enjoying the new ride. I'm still getting used to three pedals, but I've finally encountered a minor issue other than the usual rattling of things on a 19-year-old car. After I've been driving for more than about half an hour, I notice the car idles at about 1000 RPM. This isn't really a big deal, but the repair manual says that it should idle between about 650 and 750. When I turn the car off for a few minutes and back on, it does go down into the 700 range, but it eventually hoes back up to 1000. It's not surging at all, but it is above average, so I'm interested in what's causing it and how to fix it.

[spiffyguido]

Any codes on the ECU?

viewtopic.php?f=3&t=14

[elspectro29]

Other than the IAC, would there even be a code listed that would cause this?

[spiffyguido]

ECT might cause that. So might the EACV (if so equipped).

Are you getting any codes at all?

Also, when was the idle last adjusted? Idle problems can sometimes be caused by mechanical problems. On an '86 lude I had I had a high idling problem that turned out to be a sticky throttle body butterfly. This was very hard to diagnose, because it would only get stuck slightly open some of the time, leaving me scratching my head as to what was causing the problem.

[elspectro29]

I haven't been able to check yet, but the CEL isn't on, so if it's a problem that shows up on the ECU it's a minor one. I don't know when the idle was adjusted, since I've only had it for a month. My thought is something's getting stuck, because it occasionally will drop back down to normal idle at a light. It's also not exactly at the same RPM at every stopping point. Sometimes it's about 900, sometimes right at 1000, and sometimes about 1050.

[spiffyguido]

Sounds like it could be the throttle butterfly. That's similar to the symptoms I had.

Simple test:

When the engine normally encounters the problem, hit the gas and then let your foot slip off the pedal so that the spring in the throttle body can slam the butterfly shut. In my case, this was enough to overcome the sticky section. If after doing this the idle is normal, then you probably just have a sticking throttle butterfly.

Also possible to do this test by using your hands on the throttle spindle on the throttle body. Open, and then let it slam shut.