I have a 1988 Civic automatic transmission. Sometimes when I start it the idle is fine, 700-800 RPM in gear. Somtimes the Idle is to high 1000-1500 in gear. I just never know what it is going to do untill I start it. Does anyone have an idea why it does this??
Jerry

 

Is the high idle occurring when you first start the car?

 

Yes and it will stay that way untill I turn it off. When I restart it it may or may not be high. I never know untill I start it. Sometimes it idles correctly and other times it idles high. I concerns me because of the high RPM at highway speeds. When it is running correctly the RPM is 3000 at 60MPH. when it is high it is 4500 at 60MPH. Weird, huh!

 

Anyone know about something called idle memory. I think it has something to do with pulling some fuse for a time and then putting it back in.

 

not 100% on that, you could disconnect the battery for like 30 mins and put it back in (resets ECU i believe) then let it run for like 15 mins in drive way and it will reprogram the ECU.

 

The main reasons for too high / unsteady idling are:
Dirty IACV
Sticky throttle cable
Cooling system not completely full of coolant
Vacuum leaks

Clean your IACV (Idle Air Control valve, also called Electronic Air Control Valve). Sounds like it is sticky. If you have the DPFI system, the IACV is on top of the intake manifold near cylinder #1. The medium sized hose from the side of the air box feeds air to it. If you take the cover off of the air box and stop up the hole for that hose, the engine should slow down and almost die. The same thing should happen when you unplug the IACV wire.

 

I have disconnected the battery, when I reconnected it did seem to work and the idle did correct itself, although it did not last for more than a week. What might I have to replace to get it to maintain idle memory?

 

is there IACV cleaning DIY guide(civic 97-98) with pics how to do this ? im surely interested, we have similar idle problem and car.

 

On my 1988 civic 1.5 liter, if the timing belt goes out will the engine be ruined? Also on my idle problem, I replaced the EACV and still have the same problem. Could I need a new computer?