I need help. Last week I've been getting high idle. 2002 3.0 5 speed manual.
When I depress clutch the idle races to 2500-3000 rpm. Then will drop slowly but happens on every shift. I replaced the IAC valve to no avail.
For what it's worth, the clutch was replaced a couple weeks ago but I don't see how this could have any effect.
Any help would be appreciated.

 

I'm thinking about the throttle cable or throttle body. I'm thinking those areas. To check the throttle cable. Go to the floor and gas pedal. Find out if there is slack in the cable or if it is to tight. Throttle body. Chase the tube from the air cleaner to the end. Remove it there and you are at the throttle body. Hope I helped. Manuel's I don't know much about.

 

Couple of things to check

Yes, make sure throttle cable or cruise cable is not hold throttle open.

Also unplug the 3 wire connector on the TPS(throttle position sensor) and check it for corrosion.

Normal operation on cold start will be idle at 1,100-1,200 depending on outside temp
Idle should then slowly drop to about 700 when engine is fully warmed up
If warm engine idle is higher then you have a vacuum leak, and a vacuum leak can also cause your symptoms.
After engine is warmed up and idling, unplug the 2 wire connector on the IAC Valve
RPMs should drop to 500 or engine may even stall, either is good it means no vacuum leak
If RPMs stay up then there is a vacuum leak


Remove throttle cable and cruise cable from throttle linkage
Manually open throttle fully and then let it "snap" closed, throttle plate needs a good spring to force it closed at higher RPMs.
The force of the air coming in will hold it open, and with No Load/clutch pedal down, engine RPMs will go up if throttle doesn't start to close when you let your foot off the gas pedal.


Also, after engine is warmed up, turn it off and then unplug the IAC Valve
Start engine, you will have to "give it some gas" to keep it running because IAC Valve will be closed.
Take it for a drive to see if you still have the high RPM issue.
If so then IAC Valve is not involved.
If you do NOT have the problem and IAC Valve is new then computer is opening IAC Valve and holding it open when it shouldn't.
Get your VIN number and stop by a Ford Dealer to see if there is a Software update for your Ranger, if I remember correctly there were issue in the early 2000's for similar issues on many Ford engines

 

Thanks, I'll give it a try

 

OK so I tried unplugging the IAC connector and the idle didn't change much at all. But while monkeying around with the TPS sensor, by chance I noticed that the idle jumped significantly just by moving the wires on the connector. I could move them around and the idle would surge and drop. Hopefully it's as simple as changing the harness?

 

TPS works similar to a light dimmer or volume control, it is a variable resistor.
It gets 5volts from Computer on the top wire.
It sends back Throttle Position Voltage on the center wire
.69 to .99volts is closed throttle, under 1 volt
Above 4.5volts is Wide Open Throttle(WOT).

The 5volts on top wire is shared by several sensors, MAF, IAT, ECT included.

You can use a Volt Meter and a sewing pin to test voltage in the wires
TPS should be plugged into its wiring, Turn on the key
Insert sewing pin into top wire, should be 4.8 to 5.2volts
Pull out the sewing pin and insert it into Center wire, should be under 1 volt, move wires around
Also open throttle manually and watch the Center wire voltage, it should climb up steadily, no jumping or dropping voltage, STEADY is the key word.
At WOT is should be above 4.5volts

Lower wire is a Ground but don't use it for this test

 

Just an update. After chasing this problem for a while, it turned out to be a leak in the pcv hose. Replaced the hose and pcv valve and all is good finally!

 

Good work

Thanks for the fix and the update