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Thread: C4500 high idle at cold startup

  1. #1

    Default C4500 high idle at cold startup

    Started the C4500 this morning at about 18 degrees. Truck started normally, then after about 5 seconds, revvs to 1500 RPM and exhaust brake actuates (?) with switch in 'OFF' position.

    Not liking the roaring fast idle on a cold engine, I step on the accelerator, and idle comes back down to normal. After a few seconds, it revvs back to 1500, and exhaust brake actuates...

    5 minutes or so of this, and finally the truck is warm enough to where input from the footfeet keeps it at a more reasonable cold idle.

    I have heard of cold high idle settings, but this seems WAY too fast for a cold engine, and wondering what the exhaust brake acutation is all about?
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  2. #2
    Join Date
    Jan 2001
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    Default

    Did you figure it out? My 06 2500 has some sort of fast warmup function that raises the idle and closes the vanes in the turbo to speed warmup. I don't have it enabled, so I don't know if it's exactly what you're seeing, but it sure sounds the same. It cuts off if you touch the throttle. Oh, and we don't have exhaust brakes... Wonder if EFI live could make one for me?
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  3. #3
    Join Date
    Jul 2007
    Location
    ortonville, mi
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    Default

    it's actually better for a cold engine to idle that high when cold, the oil is thick and harder to be "thrown" up to the cylinders to lube them, the exhaust brake kicks on to restrict the exhaust to aid in warm-up

    if it's like what my LBZ does, it waits a few before it kicks up the idle, giving it a chance for oil pressure to come up
    http://www.thedieselpageforums.com/tdpforum/image.php
    07 GMC CC SB LBZ
    70 monte carlo, original 4 spd, bench seat
    71 monte carlo SS clone, street/strip
    97 grand am, beater

  4. #4

    Default

    I've decided to trust the GM engineers and let it be. Seems odd, however, that it will return to the fast idle after the truck has been driven 100's of miles and has been warm for many hours. Will do it when temps are in single digits and truck is sitting during a delivery stop.

    ???

    Probably need to have a winter front made for the truck.
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  5. #5
    Join Date
    Jul 2007
    Location
    ortonville, mi
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    Default

    the engines cools down cause it's not working (underload) when it cools down to a specific temp, the computer kicks the high idle back on, our 2000 powerjoke does the same thing
    http://www.thedieselpageforums.com/tdpforum/image.php
    07 GMC CC SB LBZ
    70 monte carlo, original 4 spd, bench seat
    71 monte carlo SS clone, street/strip
    97 grand am, beater

  6. #6

    Default

    This function wastes LOTS of fuel. I am limiting warmup time, and starting and stopping the truck even during short stops, instead. The idle is too high, the air brake noise too loud if in my residential driveway at 5:30 AM, with neighbors still sleeping.
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  7. #7
    Join Date
    Jan 2001
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    Default

    On the 2500 you can disable it through the DIC. Don't know if you're so lucky...
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  8. #8

    Default

    DIC-less.
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  9. #9
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,573

    Arrow

    Quote Originally Posted by Mark Rinker View Post
    DIC-less.

    That's unfortunate.

    But you do have a PTO throttle control, don't you? If so, set it at a lower RPM (800?). It should override the high idle.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  10. #10

    Default

    Yes there is a PTO throttle control switch. Since I don't have a PTO system, it doesn't get much use. The first trip out with the truck, I bumped it and it took me awhile to figure out why my truck wouldn't go very fast...
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  11. #11

    Default

    The PTO switch does override the high idle. Thanks for the info, DMax its always fun to learn a new trick...
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  12. #12
    Join Date
    Jan 2001
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    New Hampshire - Live Free or Die
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    6,057

    Default

    Just for grins, I turned mine on. It's actually sort of neat. Definitely speeds up the warming. Before it really didn't make sense to let it warm up because it didn't warm up. Now it does. And the whistle is sort of cool, too!
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  13. #13
    Join Date
    Sep 2006
    Location
    Anchorage, Ak
    Posts
    215

    Default

    my '05 5500 lly does the same thing. when I start it it runs for a min then bumpes up to 1200-1500rpm until it reaches normal temp then drops to normal idle. if it cools off(idling in -20) it will bump back up to make heat. I thought it was a bit fast for a cold motor to, but its a normal thing so I figured oh well.
    Main rig-1978 chevy 3/4 f/t 4x4 8" lift 38 14.5 16 toyo m/t's. BUILT 350(soon to be 6.2) quad batteries. front and rear 15k winches. lockers F/R. dana60 front full float corp 14 rear. th400/np203.

    donor rig. 1988 GMC K3500 140k miles, th400. IFS(read CRAP) semi float 14 rear. drove it 142 miles home at 17mpg and 1/4 quart of delo 400.

  14. #14
    Join Date
    Feb 2008
    Posts
    31

    Default You can turn it off.

    You can turn this feature on and off I believe...I remember seeing something in the manual about it. My 07 C4500 does the same thing.

  15. #15
    Join Date
    Jan 2001
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    New Hampshire - Live Free or Die
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    Default

    Mark:

    did you ever figure out how to disable this?

    Try this:

    Key on engine off.

    Depress the accelerator to the floor and hold it.

    Apply the brake 3 times in 8 seconds.

    Release the accelerator and start the engine.

    (Hope I got it right...)

    This will toggle the feature on and off on the 2006 2500/3500 without DIC.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

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