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Old 02-02-2015
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Join Date: Feb 2015
Location: Lancaster,Ohio
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Icon5 500 Rpm?

I got a idle rpm question on my 2001 ford ranger, 2.5 4cyl Manual Tranny
I adjusted the idle screw a while back and it had an check engine light. went to the auto store and they said it was the IAC. So i bought a new IAC and replaced it. it still had an check engine light after resetting the computer. so i thought this all started with the idle screw. so i put it back to its original position. no check engine light anymore but now it idles around 740-500. It will dip down to 300 for a split second when i press in on the clutch then it will go back to 500.

Is this normal?

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Old 02-02-2015
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There are no idle screws on fuel injected engines, no jets.

What you are adjusting is an anti-diesel or anti-stall screw, it can also be used to adjust minimum voltage on TPS(throttle position sensor), which needs to be .7 to .9volts, that may have been the cause of the CEL(check engine light), you lowered the TPS voltage too much or raised too much.

Since fuel injection doesn't use jets, adjusting the air flow doesn't suck more fuel in, it just leans out what computer is sending in.
So an IAC(idle air control) valve is used so computer can set idle without leaning out the mix.
IAC valve is used on all fuel injected engines, it isn't just Ford, if it doesn't have a carb it has an IAC Valve.

To properly reset this screw, it you are not sure where it should be, warm up engine, and then unplug the IAC valves wires, IAC Valve will close all the way.
Idle should drop to about 500, or it may stall, either is usually fine.
If idle is higher then computer can't set minimum idle because screw setting is allowing to much air in, or you have a vacuum leak, very common issue for erratic idles.

Warm engine target idle for manual trans is 650, automatic 750

Pushing the clutch in will often raise the idle, it will also hold RPMs high for a few seconds if you are moving, computer is doing that on purpose.
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