I had a fairly long answer but the page froze-up. So now I will just say 600-700. I have three z24's and two more in the family.They all idle close to 650 rpm's.
Test the throttle position sensor, then the Idle air control valve you may find your solution here....
If the 1998 Olds Achieva will not rev over 2500 rpm there may be an issue with the idle control valve. A bad or unplugged valve will not let the car accelerate over 2500 RPM.
I have the same problem with my 98 Isuzu Rodeo. If you haven't already, replace the Idle air control valve. I have the same problem with my 98 Isuzu Rodeo. If you haven't already, replace the Idle air control valve.
The idle speed is computer controlled
I'd take a guess that maybe your vaccum hose may have a leak? or it's even possible that you could have something wrong with your idler (programming)
Idle is controlled by the ECM (computer). Not adjustable. check sensors
It sounds like the IAC valve which is very easy to change on the 97-98 models but first check to see if there is a vacuum leak. Hope this helps. The IAC is the Idle Air Control valve and is on top of the intake manifold driver's side.
It is not adjustable. If the idle speed is not correct, then you have a sensor/actuator/computer issue.
Get the throttle checked.
132 hp (98 kW) at 5600 rpm with 130 ft·lb of torque at 4600 rpm.
on throttle boyy in corner
The choke mechanism on your 98 Explorer could be sticking. The EGR valve could also not be functioning right. Either of these issues could cause the rough idle problem.