I test drove a Ranger the other day that I'm looking at buying. It's a 1998 4.0 ohv with an auto tranny. When I accelerated there was a noise coming from somewhere. The noise is like a jet engine starting up, it's somewhat high pitched, but only lasts for a short time.

During acceleration you would hit 1500 rpm's and the noise would come and then you'd hit 2000 rpm's and the noise would go away. Keep in mind, the noise occured only during acceleration, and no other times (you could be going 65 mph and the noise will not occur as long as you aren't acceleratin. If you had it in park or neutral, the noise would not occur at all when you reved the engine.

Could it possibly be something with the driveshaft? I was thinking wheel bearings, but that would be more of a grind and the noise would happen whenever the wheels move, not just during acceleration.


I'm getting it checked out my a mechanic this week, I would just like to get a heads up. When the guy bought the car, the dealer said it was just one of those noises that occurs. He bought it and has been driving with the noise for a year and nothing has gone wrong with the car, it works just the way he bought it. The dealership also knew about the noise when they got it and looked it over, there was no sluggish performance or anything going wrong.

 

Hey i hear that same high pitch noise on my 1999 ford ranger. I've been hearing it for a while but my truck seems to run perfect. Did u u get it looked at?

 

The screaming banshee happening at idle and up to 2k rpm most likely is the IAC needing to be cleaned or replaced.

About a 60 dollar part. It controls idle speed.

 

Cool, thanks for the info I'm gettin it checked tomorrow so I'll let you guys know what it is

 

what exactly is the IAC..and it seems like on mine it doesnt make that high pitch noise at idle but it seems like it makes it right before it shifts to a higher gear.

 

Idle Air Control

It is a valve that controls the air airflow at idle.


Right now my truck sounds super charged due to the power steering pump going out.


Its really hard to diagnose sounds over the internet. The IAC is easy because it literally screams like a banshee when the truck is hot and idling.

 

ok...i looked up idle air control online and i saw that i can clean dirt out from inside it. ill have to try it tomorrow. Thanks for the help.

 

FWIW, when I cleaned mine it got worse. I sprayed some silicone lube into and that seemed to clear it up.


These things go bad and cleaning is really a band aid but if it works its great.

 

Well now that I listen to it more carefully, its like a high pitch chatter (like a squirrel). I was ocncerned about rod or spark knock, but that would happen all the time, not just in drive. I bought the truck anyway.

 

If you're still reading, he's what's probably going on: Valve rockers and upper pushrod tips still received poor oil supply, resulting in eventual wear to these areas, and consequential valvetrain noise as a result of the increased clearance.

The Ford Ranger 4.0L Engine - The Ranger Station