Author Topic: 2001 6.0L really low idle all of a sudden  (Read 18739 times)

Offline zieg85

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2001 6.0L really low idle all of a sudden
« on: December 27, 2015, 04:51:19 PM »
I just picked up a truck to run back an forth between my 2 places (roughly 300 mile one way).  I bought this 2001 2500HD with a 6.0L 5 speed standard yesterday and had no problems driving it the 120 miles home.  Today I drive it to my brothers house to change the tires and now it barely idles and dies pretty often.  No check engine light but now the tach shows it idling around 400 rpms where yesterday it was 6-700.  I was looking for a vacuum line that may have come loose but could not find any.

Anyone got any suggestions???  Thanks in advance.  It does not have AC BTW, just a plain old work truck...
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline Irish_Alley

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Re: 2001 6.0L really low idle all of a sudden
« Reply #1 on: December 27, 2015, 05:26:50 PM »
cant help you but we might have to start a new board just for these "new" trucks lol. i was kind of surprised when i went to check the gas millage on my 02 and its getting mid 14s. my crew cab gets better than that
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Offline Irish_Alley

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Re: 2001 6.0L really low idle all of a sudden
« Reply #2 on: December 27, 2015, 05:27:34 PM »
i think i need more power lol but...... its the wifes truck
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline zieg85

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Re: 2001 6.0L really low idle all of a sudden
« Reply #3 on: December 27, 2015, 06:18:09 PM »
i think i need more power lol but...... its the wifes truck

About 3 years ago I looked at a 99, same drivetrain.  It was a dog for power.  This one moves rather nicely IMO.  Ole blue (1984 C10) is down at the new place and the knock I only heard, I now feel in the clutch pedal so it is not going far. 

I don't hear any vacuum leaks but it should idle higher than 400 rpm
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline Jason S

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Re: 2001 6.0L really low idle all of a sudden
« Reply #4 on: December 27, 2015, 06:44:59 PM »
No check engine light but now the tach shows it idling around 400 rpms where yesterday it was 6-700.
A similar issue occurred with our '01 Tahoe several years ago.  Took it to the dealer and was diagnosed as carbon buildup in the intake/throttle body, they also flashed and updated the computer at that time. No troubles since then.
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Offline zieg85

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Re: 2001 6.0L really low idle all of a sudden
« Reply #5 on: December 27, 2015, 07:56:41 PM »
Thanks Jason S for the reply, that might be all it is.  Just sucks that it would happen the 2nd day I got it and it only has 121K miles
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline Irish_Alley

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Re: 2001 6.0L really low idle all of a sudden
« Reply #6 on: December 27, 2015, 08:18:27 PM »
your truck looks more of a truck than my truck lol. i need fender flares and maybe make a new bumper
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Offline LTZ C20

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Re: 2001 6.0L really low idle all of a sudden
« Reply #7 on: December 27, 2015, 08:54:46 PM »
Carbon build up on the throttle body is completely normal, it happens to all vehicles, carb or efi, it's the black stuff that turns gold colored butterflies in the carb or bore of a throttle body black. Fuel injection services are recommended every 30 thousand miles. This includes flushing the injectors, add a cleaner to the fuel tank and clean the throttle body and relearn the idle. This can be done at home.

Simply remove the intake duct from the throttle body, using throttle body plate and bore cleaner and a red shop rag, spray the cleaner on the butterfly and the rag, scrub both sides of the butterfly until it is as clean as you can get it, do the same to the bore of the throttle body. The throttle body should be aluminum color when clean and the butterfly plate gold colored. When both are clean, reattach the intake duct, start the engine. It will have a high idle, to learn the idle, drive the vehicle for at least 5 or 6 miles coming to numerous full stops allowing the engine to return to idle before starting off again. Do this alot, it's going to relearn the idle speed. If the idle doesn't relearn after this operation. Disconnect both battery cables, touch the cable ends together for about a minute. Then let it sit for another 5 to 10 minutes with the battery still disconnected. After the time has passed, reconnect the battery, restart the engine and drive it again for another 5 or 6 miles again making numerous full stops to idle. Then add your choice of quality fuel treatment to the fuel tank. Following the instructions of course. I recommend using Standadyne fuel system treatment for gasoline engines or fuel system cleaner and throttle body cleaner from BG Cemicals, preferably BG Chemicals. We use BG products at work and they are very good. The fuel additive is called BG 44K Fuel System Cleaner and the  throttle body cleaner is called BG Throttle Body & Intake Cleaner.

Or you can take it to a dealer. Just a fuel injection service is relatively inexpensive.
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Offline Engineer

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Re: 2001 6.0L really low idle all of a sudden
« Reply #8 on: December 27, 2015, 08:56:30 PM »
Clean the throttle plate, the IAC motor, and the IAC motor passages. Use carburetor cleaner to clean it all off. You will have to take the IAC motor out of the intake to do it right. It will most likely be covered in gooey black slimy carbon.

If cleaning all of that doesn't fix it you may need a TPS (throttle position sensor).

I recently had to replace the TPS on my wife's 2001 2500HD. Hers has a 6.0L engine as well. However her issue was a high idle. Like 900~950 RPMs.
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Offline zieg85

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Re: 2001 6.0L really low idle all of a sudden
« Reply #9 on: December 27, 2015, 09:02:51 PM »
Awesome Gents!!!!  Thanks a bunch!
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline Irish_Alley

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Re: 2001 6.0L really low idle all of a sudden
« Reply #10 on: December 27, 2015, 09:36:03 PM »
one common problem that im seeing is the fuel pressure regulator. idk if it could cause your problems but mine will take some time to start up when cold and every once in a while i smell gas coming from the engine bay
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When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Irish_Alley

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Re: 2001 6.0L really low idle all of a sudden
« Reply #11 on: December 27, 2015, 09:38:47 PM »
the way i understand to test is by unplugging the vacuum line and if fuel comes out then the regulator is bad. 55-62 psi
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Offline LTZ C20

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Re: 2001 6.0L really low idle all of a sudden
« Reply #12 on: December 28, 2015, 10:02:46 AM »
Clean the throttle plate, the IAC motor, and the IAC motor passages. Use carburetor cleaner to clean it all off. You will have to take the IAC motor out of the intake to do it right. It will most likely be covered in gooey black slimy carbon.

If cleaning all of that doesn't fix it you may need a TPS (throttle position sensor).

I recently had to replace the TPS on my wife's 2001 2500HD. Hers has a 6.0L engine as well. However her issue was a high idle. Like 900~950 RPMs.
You only have to do this if there is an issue with it or the ECM is setting a code for it. If it's not then, don't worry about the IAC. We don't see many problems with those much at all.
LTZ Cheyenne C20

Offline LTZ C20

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Re: 2001 6.0L really low idle all of a sudden
« Reply #13 on: December 28, 2015, 10:46:56 AM »
one common problem that im seeing is the fuel pressure regulator. idk if it could cause your problems but mine will take some time to start up when cold and every once in a while i smell gas coming from the engine bay
We don't see much of this either very much. Again, only of the failure conditions exist.

For your concerns, we see dirty throttle bodies more than anything and we see them all the time. It's the best place to start and the conditions of a dirty throttle body match your complaint.

That is the first place you should start.
LTZ Cheyenne C20

Offline Irish_Alley

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Re: 2001 6.0L really low idle all of a sudden
« Reply #14 on: December 28, 2015, 09:22:51 PM »
Any update ?
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes