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

[Monty in Calgary]

Hi everyone. Need some help with a problem. My 2006 Ranger Sport seems to be idling too low, about 730 RPM. At red lights, at resting idle, it drops pretty low, the engine kinda shudders, the engine light starts to flash. When the traffic light turns green, I can't get more that maybe 10 k/hr out of her for several seconds, then she recovers and the engine light goes off. Anyway... for the last few weeks, I've been "two-footing" at stops.... holding the truck with the brake while also just ever-so-slightly keeping the accelerator depressed, keeping the revs just a touch above 750 RPM (between 750 - 800). Since I've been doing that, I haven't had a single problem, nothing.

I know there are other likely causes for the idle problem, like the IAC, maybe a vacuum leak, maybe the PCM needs to be flashed, and so on.

What I'm looking for, here, is a way to temporarily adjust the throttle cable, mechanically, so that when I stop at a red light and release the throttle peddle, the actual accelerator cable stops JUST short of 100% release, so that I can get that slightly elevated rev without having to do it with my foot, just for as long as I need to to figure out the proper solution. I figure there's probably some way to use zip ties on the cable itself, or maybe some kinda clamp to affix somehow under the hood that stops the rocker at the end of the cable from going ALL the way back, but I can't figure exactly how to do either, of if there's another way to do it that would work.

I've included a couple pictures of "under the hood". If you look, can you also tell me if the IAC is that round piece with the electrical connection plugged into it? (bottom half of picture, slightly to the right, above large rubber hose, with a red and a white wire). I'm guessing it is.

Anyway, folks.... any ideas/guidance would be most appreciated! Thanks, in advance. Monty

 

[Curious Hound]

There is a throttle cable zip ties mod documented in our tech library. The zip ties go down at the pedal end of the cable. But it would be far better to fix the problem. Most likely the IAC. Easy to test. Easy to clean. Easy to replace.

 

[RonD]

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

 

[Dirtman]

Hey man I've been broke before but seriously you can just take the IAC valve off and clean it for free to see if you can fix the problem. Sometimes they are just gummed up and stuck closed.

Or like Ron said, grab one from the junkyard for like $5 bucks.

Or stick a needle in a vacuum line... Please don't go messing with your throttle cable.

 

[Monty in Calgary]

There is a throttle cable zip ties mod documented in our tech library. The zip ties go down at the pedal end of the cable. But it would be far better to fix the problem. Most likely the IAC. Easy to test. Easy to clean. Easy to replace.

Did the "test" for the IAC (unplugged/plugged, compared RPM). It dropped 500 RPM when unplugged and returned to around 750 when re-plugged.
I see someone else mentioning about "cleaning", as you did. Sounds like it might be a thing to do, as soon as I figure out how to get it off, etc.

Thank you.

 

[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 tested the IAC valve (unplug/plugged in, compared RPM) RPMs dropped around 500 RPM when disconnected and went back to around 750 when re-connected. From what I've read, I believe that means it PASSED the test, right? Might it still be worth replacing, despite that?

Been looking at every hose under the hood for cracks, looseness, etc. Haven't found anything.

Idle is NOT low when starting engine cold.

About that "anti-diesel" screw... I have a question.... Given that the amount of RPM I'm trying to leave the throttle at is such a small amount (just a few TENS above where it is, so bringing it from 750 to maybe 800, ideally), if I made that anti-diesel screw adjustment for just that tiny bit, would you think it might STILL constitute a problem, long term? Asking because I don't know, for sure, if I'll EVER manage to get this fixed.

I should explain something that may be confusing. I say the normal idle is at 750, but I mentioned 730 earlier. What I'm trying to say is that if I stop a very short time, just a moment, she tends to settle at 750, but if I sit for more than a minute or so, it tends to start to fluctuate and I see it drop to around 730 and that's when problems begin. That why I've been two-footing to keep her "just" above 750, usually around 800.

One last question, if you still have a moment.... (don't want to overstay my welcome).... How likely would you think the PCM could be the culprit? I've been told that there's a PCM "re-flash" that can be done that might kinda re-set it, if it's misbehaving, and fix it all up, but I'm also told getting the dealer to do that could cost me $300 and might all be for nothing, which is why I'm hesitant to do it.

Oh man, I'm sorry I'm writing a book here. Don't mean to monopolize your time. It's just that I've already spent several thousands of $$ on this used truck (just bought November, 2020) and I'm to where I'm desperate to try and make her work and be worth the painful amount I've spent. I seem to have everything good, now, but for this idle problem, so I'm VERY thirsty for a solution, and information from knowledgeable folks, such as yourself, is so darn helpful.

 

[Curious Hound]

I think there's a good bit of troubleshooting to do here before jumping to something as drastic as reflashing the pcm. Since you mention it's fine when engine is cold and not fine when engine heats up points to the engine coolant temperature sensor as RonD mentioned. Also, it would be good to check for engine fault codes. You can get that done at a parts store or buy a Bluetooth OBDII adapter and use that with a free app on your smartphone to read codes.

 

[Monty in Calgary]

Hey man I've been broke before but seriously you can just take the IAC valve off and clean it for free to see if you can fix the problem. Sometimes they are just gummed up and stuck closed.

Or like Ron said, grab one from the junkyard for like $5 bucks.

Or stick a needle in a vacuum line... Please don't go messing with your throttle cable.

Thanks. I get the throttle cable "fix" isn't preferred and I'll avoid it if I can fin another solution. I'll try getting the IAC off and clean (or replace) it, as you suggest, first, for sure.

The "needle in a vacuum line" bit. You mean to maybe introduce a small hole/air leak into an appropriate line?

Thanks for the concern. Appreciated.

 

[Dirtman]

Yes it was half a joke but vacuum leaks increase idle rpms, I'd take a vacuum leak over messing with the throttle cable. Last thing you want is screw with the cable and it gets stuck while driving.

This does not include the ranger stretched throttle cable fix which involves zip ties under the throttle pedal, this isn't holding the throttle open at all it just takes up slack. This trick won't help in your situation anyway. This is what @ericbphoto described. What this does is make is so you can get full throttle again. It doesn't fiddle with idle.

@RonD is the resident genius but remember what he said, messing with that anti diesel screw screws up the TPS sensor. It'll work but horrible way to fix it cause it introduces another issue and you will need to reset it later which sometimes requires a multimeter unless you can put it back EXACTLY where it was.

 

[Curious Hound]

It doesn't fiddle with idle

It does if you add too many zip ties.

 

[Dirtman]

It does if you add too many zip ties.

I put one too many on mine and it just broke off. It lifts the throttle pedal and doesn't actually pull the cable out? Dunno how it could screw with the idle if done right (aka pull up the pedal and stick them behind).

 

[Curious Hound]

I put one too many on mine and it just broke off. It lifts the throttle pedal and doesn't actually pull the cable out? Dunno how it could screw with the idle if done right (aka pull up the pedal and stick them behind).

I didn't think of that.

Oops.

 

[RonD]

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

 

[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

I don't appear to have this on mine. There's a little "tit" there that the throttle butts up against when it's fully released, but I see nothing there like a screw or anything that can adjust that "tit's" position. Wish there was. I'd push that tit out just a smidgen. All I'd need it perhaps the width of a dime, it's that close.

I took the IAC off, intending to clean it, but there's really nothing there to clean. Question, tho.... I noticed there's no gasket under the IAC. Shouldn't there be one? I would have thought so, and...... if there SHOULD be a gasket, and its missing, could THAT affect the function of the IAC?

 

[Monty in Calgary]

There is a throttle cable zip ties mod documented in our tech library. The zip ties go down at the pedal end of the cable. But it would be far better to fix the problem. Most likely the IAC. Easy to test. Easy to clean. Easy to replace.

Thanks. I did the test of the IAC by unplugging, then plugging, and compared RPM. When unplugged, the RPMS dropped about 500. Went back up to about 750 when plugged in again. From what I've read, that seems to be a "pass" for the IAC.

Took the IAC off, intending to clean it but, frankly, I didn't see anything to clean. Was expecting some buildup or something, but didn't. I did notice that there was no gasket under it. Should there be one??? And, if there should be one, but there isn't, would THAT negatively affect how the IAC works?