2.9 Auto correct idle RPM?

[Kellogg]

Hey guys, need some help! I have looked through the 2.9 specs page and through the forums and couldn't find a definite answer. When i first got my truck, it took forever to warm up and had a really high idle (1500+) and would bang hard as hell when put into gear. Over the past year or so i have replaced one at time: map sensor, IAC sensor, coolant temp sensor, O2 sensor, spark plugs, wires & cap, all EGR components, throttle position sensor, all vacuum lines, purge solenoid, and check resistance on ALL sensor wiring back to computer with no one component having a significant effect. What made the biggest difference was playing with the idle adjustment stop screw. I was able to bring idle down to 800 when fully warmed. it still can take almost 5-8 minutes for idle to come down and stay down especially when cold outside. Is that normal? and is 800 rpm normal? my idle adjustment screw is as far out as it can go without engine stalling when shifting into gear and every now and then it still shifts hard into reverse. Had my mechanic drive the truck around with me and he said he thinks 800 is still too high. I know the A4LD’s can be goofy as hell. Sorry for the long post.

 

[rusty ol ranger]

Dont screw with that screw.

850 in neutral is normal for an automatic (manual is 650), and 5 minutes isnt to long for everything to kick into closed loop (warmed up) operation.

 

[adsm08]

You have an air leak somewhere. You need to find it, fix it, and then reset the idle. By messing with the idle already you have made finding the leak that much harder.

The procedure for setting idle speed on a 2.9 is to warm it up fully, then shut it down. Unplug the SPOUT jumper and IAC, and replace the PCV valve with a "calibrated orifice" (the one for the 2.9 is about .020", so I just held my finger over the hose and left a little bit open) run it at 2000 RPM for 5 minutes, then return to idle and then use the screw to set the idle to the proper RPM.

But Rusty is right, when it hasn't already been touched by an idiot, don't touch the idle screw on an EFI engine. EVER.

Edited to add forgotten steps.

 

[Kellogg]

Thanks guys, point taken.

Forgot to mention that i recently replaced the PCV valve, grommet & hose, fuel presser regulator, and removed & cleaned upper and lower plenum/intakes, and give it new injectors. BUT by that point i had already messed with the idle screw from its original setting from when I got the truck. I will try resetting the idle and see what happens. Its possible I might have already fixed my air-leak....

 

[rusty ol ranger]

The procedure for setting idle speed on a 2.9 is to warm it up fully, then shut it down. Unplug the SPOUT jumper, and replace the PCV valve with a "calibrated orifice" (the one for the 2.9 is about .020", so I just held my finger over the hose and left a little bit open) and then use the screw to set the idle to the proper RPM.

Im going to screenshot this. That way when i get around to fixing rusty 2.0 i can reset what i did screwing with that screw.

 

[adsm08]

Im going to screenshot this. That way when i get around to fixing rusty 2.0 i can reset what i did screwing with that screw.

It's good information to have, especially when you are dumb.

Ask my why I know how to do that. Just ask.

 

[alwaysFlOoReD]

OK, Why do you know how to do that?
And can you post the procedure for the old 4.0l if it's different?

 

[rusty ol ranger]

It's good information to have, especially when you are dumb.

Ask my why I know how to do that. Just ask.

Pretty sure you know how to do it for the same reason i know how to fix alot of the dumb stuff i know how to fix.

 

[adsm08]

OK, Why do you know how to do that?
And can you post the procedure for the old 4.0l if it's different?

I touched the screw. Incidentally that is also why I feel justified in blatantly calling people who touch the screw idiots.

I don't know what the procedure for the 4.0 would be. I imagine it is similar, seeing as how they have a SPOUT jumper too. Probably a slightly bigger orifice, but we are already not being precise with that, using the calibrated thumb.

 

[decipha]

there is absolutely nothing wrong with adjusting the screw

if you have confirmed no vac leaks or air leaks then its best if you do adjust the throttle stop. Your best option for doing so is to get the vehicle up to warm operating temperature and unplug the spout connector, idle air control valve connector and throttle position sensor (if you have to open the stop otherwise it will set part throttle and dump in spark raising the rpms quite a bit). Adjust the throttle stop to get it to idle as low as it possibly will without dying. Plug everything back in. Let it idle for about 4-5 min or so and it should smooth on out and be fine.

 

[adsm08]

there is absolutely nothing wrong with adjusting the screw

Except for the part where the emissions label, the shop manual, and any other service literature and instructions you can find say not to.

 

[decipha]

The emissions label, shop mnual, and any other service literature is written with the intent that the end user is ignorant and doesn't know what they are doing hence the purpose in them reading to the literature to instruct them not to.

For those more knowledgeable that fully understands how everything is designed and functions its not the case.

 

[Nez'sRanger]

The procedure for setting idle speed on a 2.9 is to warm it up fully, then shut it down. Unplug the SPOUT jumper and IAC, and replace the PCV valve with a "calibrated orifice" (the one for the 2.9 is about .020", so I just held my finger over the hose and left a little bit open) run it at 2000 RPM for 5 minutes, then return to idle and then use the screw to set the idle to the proper RPM.

Is this "SPOUT" the same one you have to unplug to set the timing, or is this the one behind the air filter box by the diagnostic connector?

 

[rusty ol ranger]

Is this "SPOUT" the same one you have to unplug to set the timing, or is this the one behind the air filter box by the diagnostic connector?

Yes. That SPOUT connector.

 

[PetroleumJunkie412]

You have an air leak somewhere. You need to find it, fix it, and then reset the idle. By messing with the idle already you have made finding the leak that much harder.

The procedure for setting idle speed on a 2.9 is to warm it up fully, then shut it down. Unplug the SPOUT jumper and IAC, and replace the PCV valve with a "calibrated orifice" (the one for the 2.9 is about .020", so I just held my finger over the hose and left a little bit open) run it at 2000 RPM for 5 minutes, then return to idle and then use the screw to set the idle to the proper RPM.

But Rusty is right, when it hasn't already been touched by an idiot, don't touch the idle screw on an EFI engine. EVER.

Edited to add forgotten steps.

There are times that I need you on speed dial.

Now I have sh*t to do to the truck in the morning. Because reasons. ?