Low idle issue

[Hammer02]

OMG no A/C at the drive thru? That's a problem in some states.Central cali summers!

How long have you owned the Denali? 5+ years

Low idle? Yup.
2002 Denali 6.0 is Drive by Wire or cable? I don't know...02-03-04 are transition years. Yes
If that picture is your TB then you are DBW. Yup.
Is this a new problem? Like when did it start (after plugs and wires? or before) End of last summer last year.
All the time? Yes all the time after warmed up.
From morning start till end of day? Yes.
At low idle is engine rough or smooth? Smooth.

No check engine light? No


Any funny noises under the hood? No

How's you battery? And alternator? 13-14v I believe..ill have to check.
How many amps are you pushing on the cluster at 500rpms. Ill have to check.
Have you hooked up a charger or booster to it and see if that changes the RPMs? No..ill try that and report back.

Is it constant at 500rpms? or does it go up and down? Is it hunting? constant.
Have you looked at the MAF? its between the airbox and tube that goes to the throttle body
Bad/dirty MAF could cause low idle (but would throw a code and hunt) Ill check this as well.

Air Cleaner OK? Brand new..changed less than a month ago.
Clogged air intake would constraint air but rpms would vary as it struggled to recover....Computer has target idle setting.....like 700 i think.
Is air intake stock or other? Stock.
Is it free of debris? Yes

Is it the stock cam? New cam can cause low/struggling idle without tune. Fully stock.

If your TB was a problem it would most likely throw a code and go into Reduced Power Mode. This hasn't happened....Yet.

How did your old plugs look when you pulled them out? They looked fairly good.
Clean? Oily? wet? Burned? Black? missing tips? or just gray and old.
Are they all completely plugged in? Its hard sometimes to get to the CLICK. 16 clicks.

What does your latest MPG say from last personal tripometer? Ill check.
How many miles do you get on a tank of gas.....
Do you run regular or premium? Reg.

There could be a connection between your A/C or other belt driven devices and your idle too. AC was checked over by AC shop...Found a leak..thats about it. Said the idle wqas the cause of it getting warm at stops.
If A/C or P/S or Alt bearings go bad it could place more load on the engine and drive the idle down.
So any funny noises? Or the bearings in the pulleys too.....they would sound aweful... Water pump and alt are new and p/s seems quiet and smooth. Ac compressor was checked and serviced by the ac shop.


Denalis are cool....stock 6.0
Shave those heads/stuff a cam in there=almost 500hp....very cool.

Wish I could!

 

[Hammer02]

Also

Bad fuel can jack with your idle (may not throw a code) (put in some injector cleaner, octane booster, or E85)
I dont know if your Denali can run E85.....E98 would be better. That would clean up a fuel issue.

Bad fuel injectors can jack with your idle (would most likely throw a code....like a p1517 lean code, maybe not)

Transmission torque converter going bad can place more load on engine (may not throw a code)

Cracked intake manifold or vaccum leak can jack with your idle (may throw a MAP code ...depends)

Things to check......

No bad fuel im sure
No codes on the injectors
Ran fuel system cleaner with premium for 2 full tanks.
Dont know about the TC but the trans feels and shifts smooth.
All vac lines seem fine
Dont know if the intake mani cracked.

 

[Hammer02]

Lastly

How does it run from idle to 5K?
Does it feel sick or healthy once you get out of idle?

She pulls as hard as ever.
kinda why I let it go all winter.

 

[Hammer02]

Wow voice to text doesn’t know how to spell Yukon Denali and I definitely didn’t poured any matches into my head lol!

I’m actually wrenching on the truck now to fix this damn mount and gloves and grease make typing impossible.,any tips? Or does everything I think I have to remove really have to come out to get the new one in clean?

I take anything thats in the way out right away..Cause If I dont It seems to end up taking longer.

 

[fasteddy]

If you've checked all your vacuum lines and everything looks good.
And your truck runs fine otherwise, you may just want to swap out the throttle body for a new one.
Maybe something is bad on the TB and not opening enough at the bottom, when your throttle pedal position is 0.

Then if that doesn't work, and if you have access to tuner software like HP Tuners, you can bump up your target idle to 900 and see if that
takes you back to 700. I've done that before....temporarily until i got the tune right on a new cam....LOL

But I'm telling ya, if you shave those heads, put in a new cam and tune it, that will fix it for sure......LOL

 

[JonnyTahoe]

on your 2002 (drive by wire) the iac is built into the electronic plastic part on the side (throttle position sensor), it's not serviceable but can be replaced, if it were me I would just replace the whole throttle there not that much. If it was a 00 or 01 it would still have a throttle cable and the iac is separate and can be cleaned.
if you are trying to save money, rockauto sells the throttle position sensor part alone (it has the iac built in to it)

About the only thing good about a '00 and '01 is the manual throttle body.

 

[Jimmyy]

K.I.S.S have you check the idle speed with a scan tool? The needle could be off on the gage. “Warm air at idle”, is the engine temperature high? Is it better with a cool engine?

 

[Doubeleive]

About the only thing good about a '00 and '01 is the manual throttle body.

I drove mine to 324k sold it about 4 years ago last time I checked it was still on the road

 

[Hammer02]

K.I.S.S have you check the idle speed with a scan tool? The needle could be off on the gage. “Warm air at idle”, is the engine temperature high? Is it better with a cool engine?

Cold it runs right
But when the truck hits near operating temp, back down to 500.

 

[fasteddy]

Cold it runs right
But when the truck hits near operating temp, back down to 500.

That's a clue!

The computer with stock tune will adjust your idle based on
1. coolant temp (over/under 90 degrees is a change point)
2. whether the A/C is on or off
3. Whether its in gear or not (Park/Neutral as opposed to Drive)

So try some combos and get back

Like
When coolant gets 180+
Come to stop
Check Idle
If 500 (stock is 550) Yours maybe lower. Without a digital gauge its hard to tell.
- turn off A/C
Check Idle
- if still 500
-put in neutral
Check Idle

Try to pin point the scenario where idle falls below operating level to run your a/c while getting tacos/burritos at drive thru.
Like can you go through the drive thru with A/C on and if you put it in Neutral idle goes back up?

When Cold or coolant under 50
- idle should be 800 with A/C on or off and in gear or not.


How long did you own it before it started doing this?

How many miles are on your 6.0L

Are you running back in AWD, or in some kind of axle delete 2WD?

You should get HP Tuners and look at the tune. If the previous owner put strange parts in it
he also may have changed the tune. People do strange things.

But your Denali worked fine after you got it then this low idle issue started to occur...correct?

But....
When I first got my Tahoe I looked at the tune for the engine and transmission.
They had "De"tuned the transmission because it wasn't shifting right due to excessive wear on some parts.
The tried to get the computer to compensate for the trans needing work.....stupid patch.