I own a 1999 Ford Ranger. About two weeks ago, the engine started acting up. While the truck is idling, the RPM will drop down very low (like .5) and begin to sputter, then shoots up to about 2-2.5 RPM, then back down to .5. Sometimes it will drop so low that I have to give it a little gas to keep it from going dead (which it has a few times).
The motor has around 150k miles I would say (engine was replaced a few years ago, so the odometer shows higher than the engine). My water pump is also going bad, but I am having that replaced this weekend.
Here is a link to a video I did so y’all can hear/see what’s going on.
Thanks for your time and any advice y’all can give.
Assuming a vacuum leak has not developed somewhere, this problem could be caused by the Intake Air Control Valve. That’s the silver widget with 2 bolts and single wire connector at the top center of the engine around the 2 minute mark.
As easy as it is to get to, you might consider just popping that one off and trying to clean the IAC before replacing it; assuming it comes down to replacement and no vacuum leaks are present.
But before you remove it, start the engine when warm, and while it’s idling take the handle of screwdriver and rap on the IAC valve. If the idle speed changes replace the IAC valve.
I had a similar symptom when my temporary kluge “fix” to the IAC on my Corolla failed. The idle speed would go up and own at random, and a lot. Made the car almost un-drivable. OP should definitely rule out the IAC before considering other things.