I have a 2001 Ranger XLT 3L V6, auto trans, rwd.

I am having an issue while idling. When I first start it up, it idles fine, around 1200-1300rpm. However, after I drive a bit and sit at a red light, my idle drops to about 900rpm. The real problem is that sometimes there is a click/knock sound, and the rpms drop to about 500 rpm then back to 600-700 rpm. I managed to capture what I'm experiencing on video.

Video:
It started happening after the most recent time I took it to my mechanic. I just bought the truck recently, and the ac wasn't blowing cold. They found that the condenser wasn't plugged in, and also needed freon. I don't know a lot about adjusting idle on cars/trucks, but my only thought is that they could have bumped into something and set the idle too low?

Thoughts/solutions greatly appreciated.

 

Looks to me like the compressor is cycling, but the idle air control valve is letting the idle drop too low. They shouldn't have messed with the idle stop screw to work on the AC, since it's behind the throttle body. But anything is possible with mechanics. More than likely, you just found out why the A/C wasn't working in the first place.

 

+1 ^^^

Fuel injected engines(any of them) can not use an idle screw, there are no "idler Jets" to suck fuel from as aid flow changes.

So all fuel injected engines use an "air valve" to set idle RPMs
Ford calls theirs an IAC Valve, idle air control valve

It looks like a can on its side and is located near the throttle linkage
It is bolted on to upper intake over an air passage that by-passes the throttle plate.
The computer controls this valve to set idle levels
A Cold engine still needs to be "choked", so computer will run a higher idle and add more fuel to a cold engine, 1,100-1,300RPM at cold start up is normal "choke" idle, it is based on the temperature of the engine, computer has its own coolant temperature sensor.
The colder the temp the higher the cold idle.

After a minute of running idle will usually drop to 900rpm or so, then over the next 5 to 8 minutes engine should reach operating temp, engine coolant at 190degF, and computer will have dropped idle RPMs down to 650manual trans or 750 automatic

Computer actively watches RPMs so it can adjust the fuel mixture and IDLE
So once engine is warmed up Target idle should be maintained, reaction time is milliseconds not seconds

If you have AC and compressor cycles on computer will raise RPMs by 50 for sure, and certainly not let it fall below Target warm engine idle, 650 or 750

So I would check and maybe clean IAC Valve

 

First, the problem has become less frequent but has not gone away all together, probably due to temps warming up in my area. I found the IAC valve and it didnt look very dirty but i used electronics cleaner on it a few times and replaced it, hasn't seemed to make any difference. I have also noticed excessive moisture on & around the compressor, and drips onto the pavement. Just water, it evaporated over night.

I've also noticed that if im idling in drive with the a/c off, then turn it on, the click & rpm drop will occur like in the video above.

 

Bump...

 

my 2003 ranger is having the same issue. Did you ever get a diagnosis or fix for it?

 

Any update on this? same clicking/idle issues here. also noticeably worse mpg.

 

His last post from 3 1/2 years ago still hasn't been answered, and he hasn't even been here for 3 years, so it's safe to say you won't get a reply.