Needs ideas, to "bush fix" the throttle cable to stop just short of full release, increasing idle speed

[Monty in Calgary]

If Warm engine idle drops to about 500 RPMs when you unplug the IAC valve then IAC Valve is OK, but could use a good cleaning
Just 2 bolts and it comes off


The Anti-diesel screw IS/SETS that 500RPMs you get when you unplug IAC Valve
So you would have to adjust it quite a bit to get 750-800RPMs as the low limit RPMs, that's what the anti-diesel screw adjusts, the low limit RPMs

Back in the old days with carbs there was a problem with warm gasoline engines having "run on" or "dieseling" after you shut off the key
It was caused by hot spots in a cylinder(carbon build up) or hot spark plug tips
When you shut off the key spark stops but if fuel is still present the hot spots can ignite it and engine will continue to "lope along"(run on) and it sounds like a diesel engine, the pinging/knocking sound, so also called dieseling
If you adjusted your idle down lower, throttle plate closed more, then less chance of Dieseling because of restricted air flow
So in the case of fuel injection its an "anti-diesel screw", because it AIN'T an idle screw, lol



Your issue reads like computer may not be seeing "in gear" and "neutral" difference
On a 2006 automatic thats done by the DTR(digital transmission range) sensor on drivers side of transmission

In Park or Neutral warm engine should idle at about 750
In Drive or Reverse, computer should bump up idle to 800
Same if AC is on, computer gets a signal and it opens IAC Valve a bit more

So after engine is warmed up shift to neutral, then to D or R, idle should go UP "in gear", when you shift, if idle drops then computer is not "getting the message"
Also turn Climate control OFF then AC on, same thing should happen if in Park or neutral, idle is bumped up

Just FYI, AC is ALWAYS ON in any vehicle unless climate control is OFF
AC off doesn't turn AC off, lol, it just doesn't cool, but compressor is still ON

So, you're saying that, "somewhere", I actually SHOULD have this "anti-diesel" screw on my fuel-injected 2006? I'll have to look again. Couldn't find it before. Also, I'll try your test suggestion, comparing DRIVE to NEUTRAL, etc, and see what happens with RPMS.

I can't use the AC bit because, in my truck, its stuck on DEFROST to the windshield, regardless of where I turn the dial. Turning it to AC (or anything else) doesn't change it at all. I'm told that's a big-cost fix. Just can't do it.

 

[Curious Hound]

So, you're saying that, "somewhere", I actually SHOULD have this "anti-diesel" screw on my fuel-injected 2006? I'll have to look again. Couldn't find it before. Also, I'll try your test suggestion, comparing DRIVE to NEUTRAL, etc, and see what happens with RPMS.

I can't use the AC bit because, in my truck, its stuck on DEFROST to the windshield, regardless of where I turn the dial. Turning it to AC (or anything else) doesn't change it at all. I'm told that's a big-cost fix. Just can't do it.

Defrost actually turns on the A/C. It helps take the humidity out if the air to clear the inside of the windshield better.

 

[RonD]

Defrost is the default setting if there is no Vacuum in the cab, easy fix

Just read in another post that 2006 may not have an anti-diesel screw, may have been deleted in mid-2000's

Defrost, panel, floor vents are all controlled by vacuum "motors", yes "they" call them "motors", lol
On the passenger side of engine bay look for a grey hard plastic vacuum line(looks like a wire), it runs to the Heater hose valve, 4 heater hoses connected
Once you find it, follow it back to the firewall
There will be Black hard plastic vacuum line coming out of firewall at that location, that's the vacuum source for the cab
Follow it, it will run to the vacuum reservoir(plastic ball) low down on front of engine bay
Make sure there are no breaks in the Black line, if so then thats your problem, splice it, it often melts near exhaust system

Black vacuum reservoir(ball) will have a 2nd black vacuum line attached, it runs to the intake manifold, follow it, all the way, if its disconnected or broken then thats the problem

You have a disconnected/broken vacuum line somewhere you just need to find it and fix it

 

[Dirtman]

I can't use the AC bit because, in my truck, its stuck on DEFROST to the windshield, regardless of where I turn the dial. Turning it to AC (or anything else) doesn't change it at all. I'm told that's a big-cost fix. Just can't do it.

Vacuum is disconnected to the hvac contols. It's not a "big cost fix", its a matter of finding the broken vacuum line or broken reservoir and replacing it. $10 dollar fix at best.

Also your AC and heat still work, they just blow out of the defrost vents because thats the default position when the vacuum control is lost.

 

[Monty in Calgary]

Defrost is the default setting if there is no Vacuum in the cab, easy fix

Just read in another post that 2006 may not have an anti-diesel screw, may have been deleted in mid-2000's

Defrost, panel, floor vents are all controlled by vacuum "motors", yes "they" call them "motors", lol
On the passenger side of engine bay look for a grey hard plastic vacuum line(looks like a wire), it runs to the Heater hose valve, 4 heater hoses connected
Once you find it, follow it back to the firewall
There will be Black hard plastic vacuum line coming out of firewall at that location, that's the vacuum source for the cab
Follow it, it will run to the vacuum reservoir(plastic ball) low down on front of engine bay
Make sure there are no breaks in the Black line, if so then thats your problem, splice it, it often melts near exhaust system

Black vacuum reservoir(ball) will have a 2nd black vacuum line attached, it runs to the intake manifold, follow it, all the way, if its disconnected or broken then thats the problem

You have a disconnected/broken vacuum line somewhere you just need to find it and fix it

Wow! I'm learning so much here! Thank you. Guess I got some "investigation" to do.

 

[Monty in Calgary]

Vacuum is disconnected to the hvac contols. It's not a "big cost fix", its a matter of finding the broken vacuum line or broken reservoir and replacing it. $10 dollar fix at best.

Also your AC and heat still work, they just blow out of the defrost vents because thats the default position when the vacuum control is lost.

Yeah... RonD just told me the same thing. I'll be hunting around for that vacuum leak. Appreciate that.....

 

[Monty in Calgary]

There is an anti-diesel screw on the throttle linkage that you can adjust that will hold the throttle open a bit more at idle

Seen under the linkage in this picture: https://www.ranger-forums.com/attac...how-do-you-remove-throttle-cable-p7190004.jpg

A little green blemish where the screw meets the throttle stop, that screw/bolt is the anti-diesel screw

You WILL need to reset this, and you will get codes and or running issues long term after adjusting it
Fuel injected engines can not use "idle screws" because there are NO JETS to suck extra full from with higher idles, which is why this is called an anti-diesel screw but "looks like" an idle screw
So there is a small risk of running engine TOO LEAN at idle, but not a problem for a few weeks
IAC Valve is used so the Computer can control idle RPMs and adjust fuel mix accordingly to avoid LEAN conditions which melts pistons and valves

Anyway, remember how much you turn this screw in to raise idle, so you can reset it after fixing the idle problem


If Idle is low when engine is cold, replace the ECT sensor first
If that doesn't fix the problem then yes, replace the IAC Valve, but you can ONLY USE Motorcraft or Hitachi brand replacement, other brands will cause other issues
A used motorcraft IAC Valve from a wrecking yard is better than any new 3rd party brand

Just reviewing the info here. I think you're onto something. I took my IAC off and cleaned it and put it back on. No difference. Noticed there was no gasket. Got one and put it on. No difference. I think I'm down to replacing the IAC. Maybe mine is just "broke" somehow.
As an aside, since I've been "two-footing" at stops to keep the idle just a hair above 750 RPM, I've gone a long time without ANY engine codes, not even the various "Misfire" codes I was getting regularly. UNTIL 2 DAYS AGO. I got a couple of those old familiar misfire codes, but for the 1st time ever, I had a different code. P05?? Can't remember. Maybe 0511? Anyway, I looked it up and there were several things mentioned, but it seemed mostly concerned about the IAC. Seeing THAT for the first time ever is starting to make me think it's likely that the IAC, itself, is the culprit here. Any thoughts?

 

[Monty in Calgary]

Defrost actually turns on the A/C. It helps take the humidity out if the air to clear the inside of the windshield better.

So, do you mean that even if it's on DEFROST, if I turn the temperature to Blue/Cold, and if the A/C system is "charged", that I should still get A/C type cold air out of it? Even without the dial being turned to A/C?

 

[RonD]

So, do you mean that even if it's on DEFROST, if I turn the temperature to Blue/Cold, and if the A/C system is "charged", that I should still get A/C type cold air out of it? Even without the dial being turned to A/C?

Yes, full cold air
AC is on or off there is no temp control for that
Temp control sends air thru the heater core, HOT, or around the heater core, COLD


If you replace the IAC Valve only use Motorcraft or Hitachi brand, they are the only solenoid IAC Valves, other brands are hybrid stepper motors

 

[Monty in Calgary]

Yes, full cold air
AC is on or off there is no temp control for that
Temp control sends air thru the heater core, HOT, or around the heater core, COLD


If you replace the IAC Valve only use Motorcraft or Hitachi brand, they are the only solenoid IAC Valves, other brands are hybrid stepper motors

Copy that! Ford or Hitachi, ONLY!

 

[cbxer55]

I've got a Hitachi IAC on both my Ranger and my Lighting. Been one both since around 2015.