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Dealer Stumped: Power Loss, Ticking Noise, Check Engine Light Under He


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#1 jasonmeredith

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Posted 06 July 2011 - 12:28 PM

I could really use some technician help. Please take a look at the video below. I've shared this video with the dealer lead tech and he's stumped.

My truck is a 2003 Silverado 2500HD 8.1/Allison. This video was taken a few years ago when towing a 10,000 lb trailer up Snoqualmie Pass in Washington. I encountered this problem only a few times until this last weekend. I now have a 14,000 lb toy hauler and was towing on much longer and steeper grades on Hwy 97 thorugh Washington and Oregon.

The video is a shot of the instrument cluster with audio. When towing on an extended grade the tranny shifts down as usual but after a short while under load at full rpm a ticking noise develops and then the engine gradually loses power until the check engine light comes on. When I back off the gas and let the rpms come way down the ticking noise goes away, the check engine light goes off, and power returns to normal. The video shows this happening above 4,000 rpms. With my heaver trailer on steeper grades this weekend I experienced the exact same situation but at about 3,700 rpm. This was 100% consistent this last weekend. As long as I keep the rpm's way down the truck pulls the heavy load on the steep grade just fine but in the 30-40mph range.The truck has about 70k miles on it. I use it exclusively for towing and winter driving. It is serviced routinely per spec. Any help would be greatly appreciated.

Ticking/Power Loss Video

Thanks,
-jm

#2 Hawkeye-08

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Posted 06 July 2011 - 01:19 PM

I expect that it does not set any codes? I didn't hear the ticking noise in the video, does it change with RPMs?
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#3 ChevyTech77

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Posted 06 July 2011 - 01:22 PM

So, only with really heavy loads, long pulls at high rpm, this happens??
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#4 Stevens11

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Posted 06 July 2011 - 01:26 PM

Possible loss of spark or spark arching/bleeding off the wires :thumbs: Years ago, I had a car that did that. Took me a while to figure it out. On a hill, under load was the only time it would do it. Turned out to be 2 bad plug wires.

Not sure if this helps or not but worth a look.

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#5 jasonmeredith

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Posted 06 July 2011 - 02:16 PM

Dealer told me no codes back in 09 but now looking at the paperwork it says "verified concern code P0300, P0134 02 senspr insufficient activity." They replaced #3 wire but said they didn't know what was causing it. I reproduced after the service but with the old 10k lb trailer it wasn't that hard to avoid the situation. I just had to keep the rpm's at 4k and i was fine.

Yes, only under heavy load on long pulls. It will not reproduce without the trailer no matter how hard you push it. Nor will it reproduce pulling heavy load on a short and steep hill. It has to run under load for about 90 seconds at 3700-4500 rpm.

The video shows it at redline with my 10,000 lb trailer. I get there easily now under 4k with the heavier, 14k trailer.

#6 ChevyTech77

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Posted 06 July 2011 - 02:24 PM

Check the plugs for oil fouling. 8100's are known to burn oil and it may not be enough to see a huge loss on the dipstick but it will show on the plugs.

Also check the plugs for signs of carbon tracking. 8100's are also hard on plug wires due to extreme heat in the plug to plug wire contact area from the exhaust manifolds. If there is carbon tracking present, it gets all plugs and all wires with a good helping of dielectric grease on the plug to plug wire connection.

If nothing is found with the spark plugs or wires I'd try a crankshaft position sensor. The 8100's were known for all kinds of goofy driveability issues steming from bad CKP sensors.
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#7 jasonmeredith

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Posted 06 July 2011 - 02:25 PM

Generally it does map with rpm, up and down. The weird thing is how it comes on and fades away. It gradually gets louder when it comes on, mirroring rpm but after I let off the gas and get the rpm's down to 3k it fades away slowly but NOT consistent with rpm. The volume decreases but the ticking slows as the rpm's remain constant.


I expect that it does not set any codes? I didn't hear the ticking noise in the video, does it change with RPMs?






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