2000 Ford Ranger 4x4; the engine jumps to 3000 rpm when sitting at a stop sign. check engine light does not come on; replaced idle sensor and master air flow sensor - still jumps to 3000+ rpm. today it stayed at 4000 rpm until engine was turned off. when started again, it was fine
By “idle sensor” I assume that you mean the idle air control motor/valve. You’d also want to check the wiring & harness for the IAC to look for problems there. The valve installs over some holes into the intake. Hopefully those passages were cleaned out when it was installed (though that would tend to produce the opposite kind of problem). The install also involves a gasket - hopefully the gasket was new or in like-new condition.
I’d also inspect the throttle linkages & mechanism for sticking and clean the throttle body.
thanks. the only thing we haven’t done so far is the throttle linkage - we’ll try that.