2.5L ('98-'01) Random / High Idle

[StimmyRanger]

Just got this truck ( 2000 Ford Ranger XLT 2.5L 4x2). Was running on 2 cylinders, but i replaced both coil packs and now shes running on all four. One issue that still remains its it idles VERY HIGH inconsistently. Let me explain.

- Start truck: idles normal, and drops even lower to normal idle when warmed up.
- Drive off: everything is normal (little slow but thats probably normal too haha).
- At a stop: Idle goes to normal but immediately raises until its probably in the 3k range (no tach)

Anyone else have had this problem or ideas to what it may be?

 

[RonD]

First see if all 8 spark plugs are working
Key off
Unplug either coil pack's 3 wire connector, move it back away from coil
Start engine
Should run fine no misfires, 2.3l/2.5l Lima engine ran on 4 spark plugs from 1974 to 1988 just fine
Shut off engine
Repeat test but with the other coil pack unplugged(yes, plug the other one back in, lol)

Any misfires means a spark plug is not working on that coil pack
You can drive it this way, it will just have less power, point of dual spark plugs is for better power, i.e. Dodge Hemi engines


Look at the IAC(idle air control) Valve on the upper intake, see if its been changed, it MUST be a Motorcraft or Hitachi brand IAC Valve, other brands will cause all sort of idle issues

Change PCV Valve, this is a controlled vacuum leak, so if faulty/sticky can cause high idles, this part is cheap and should be changed every 4 oil changes, if over 100k miles then every 3 oil changes

Higher than normal RPMs are caused by AIR coming in to the engine, not fuel
The throttle plate works by letting in more AIR not fuel, that small pedal in the cab on the right is the "air pedal" not the gas pedal, lol, always has been
So you are looking for a reason why engine is getting more air after you stop, from your description
Faulty IAC Valve can do that, same for faulty PCV Valve
But just guess's on my part

 

[StimmyRanger]

Thanks!! Ill go check on those.

 

[StimmyRanger]

Sorry for super late update, but incase this can help anyone. It turned out to be a vacuum leak.