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Old 12-27-2010, 07:29 PM   #1
TJ
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Default 2005 2500HD 6.0 no power

truck has no power towing. you can push the gas down and it wont pull up a hill until the transmission downshifts out of overdrive. it is similar in other gears when taking off from a redlight, or trying to accelerate. it hasnt done this since it was brand new. 147K on the clock.
changed plugs, wires, air filter, tranny fluid. feels like i have a brake dragging. looking into the possibility of a cat or muffler issue. it just wont rev when you give it gas. like a brick wall.

one cat is 250-280 degrees, while the other is 300-310 degrees measured all over with a laser temp gun.

the muffler is 415-450 degrees. my thinking is the cats should be hotter than the muffler, but they do merge at the muffler.

has anyone ran into this issue, whether it be a muffler comming apart, or a cat issue. ive never had either of them open, so i dont know the structure inside.

gas milage is down towing my work trailer from 11.5 into the high 9's now. its rather aggrevating.

thought it may be the fuel pump, but put a test gauge on it and beat it around the block pretty good and pressure is rock solid.
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Old 12-27-2010, 07:55 PM   #2
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no strange noises from motor/trans/transfer case/rear????

Possible that one of the knock sensors is acting up and making the pcm pull alot of timing?

How about your airfilter? replace it even if it "looks" clean.....

a clogged muffler/cats will also cause the issue you are having.... that is a possibility
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Old 12-28-2010, 09:05 AM   #3
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no check engine light? are you sure your just going crazy? lol. i have a 6.0L truck and its a slug, doesnt tow for **** and feels gutless. theyre just underpowered pigs to begin with (in a 3/4 ton truck anyway).
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Old 12-28-2010, 03:22 PM   #4
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our 6.0 is the same way 04 crew cab, 16K miles. 410 gears. its 3K rpms and not doing well or 6K rpms and still not doing well. Ive seen a friends trucks headers and mid pipes glowing orange on bone stock truck pulling a trailer with vette in it over the mountain..

With you miles it might be time for new cats.. Just get some cheap ones on e bay.. I picked up a set of 3" last year for like $50 a pop and they are leagal in all states so the "stamp" says..
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Old 12-28-2010, 04:37 PM   #5
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sounds like the cats got too hot, and there's a chunk of one of them stuck in the muffler

Pull the MAF and clean it . . .
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Old 12-28-2010, 05:21 PM   #6
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have u changed your fuel filter by any chance?
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Old 12-28-2010, 05:49 PM   #7
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no strange noises anywhere.

i dont know if it could be a knock sensor or not. dont guess that would throw a light on, so its something ill have to check. my buddy at the dealer said there was a recall on some models. the connector gets wet, corrodes and throws a false code, but i have no codes ??

air filter is a brand new wix.

no check engine light. never even flashed before.

MAF is clean.

i dont know about being a dog or gutless. i can yank anything. the only times ive ever felt like the truck was underpowered is loaded with a 8x24 enclosed trailer going up the kills of alabama-tennessee and kentucky. my truck has always had tons of power (for a gas motor) ive owned it since brand new and it has hauled anything i needed to without isse. i will agree with you on some 6.0 trucks i have driven, do feel like 4clyinder trucks, but mine doesnt hesitate. until now, obviously.

only other thing i can think of is bent fins in the torque converter. i haul a lot with it, so i dont know. it happens in hi hp race cars all the time.

thanks for all the input. ive tried to check everything i can and nothing is working. going to try and find if the local tuner has some time to hook a laptop up and see if he can see anything that looks fishy as far as injector cycle, trans line pressure, etc.
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05 2500hd. 6.0L
88 iroc-z 6.0L
one hauls, one hauls a$$.
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Old 12-28-2010, 08:26 PM   #8
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Sounds like you got a good truck.. Mike has a 05 6.0L 2500 with 205K miles all stock, never even had brakes.. He owns a construction company so it get workd hard but its a lot of highway miles.. About 180K miles it started ideling bad... would almost die. rpms drop to 400.. never a light... So i finally talked him into plugs wires and fuel filter.. fixed the rpm problem and he said it felt like it gaind 100 hp lol..

Id suggest the regular stuff, fuel filter, plugs and wires.. make sure the plugs are gapped to correct size.. i got a set last week for my sububran that where gapped at 70!

If that doesnt help it, id look into the cats.. if its been hot with some bad fuel or ethonal it might have gummed up the cats... that would be like trying to blow threw a straw.. My cats on my 8.1 where burned up at 100K miles... start spitting flakes out the muffler.. sorta looks like snow comming out..

I think those have 2.5 cats..

keep us posted. there are a lot of guy getting up there in the miles that will someday have some problems.. also hows the mass air.. If its dirty or has gone bad its like pulling a house. Mine out of the blue died in orlando on our trip to disney. no codes or light but it was as if i had 4 cylinders.. pulling out in traffice was a major challange.. 0 to 50 was around 14 seconds...

if you do get a mass air. either get one from GM $$$ or get them from autozone, but keep the receipt. they seem to only last about 9 months.
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Old 12-28-2010, 09:44 PM   #9
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we do have ethanol here in florida. almost all of the gas stations now have stickers that read "contains 10% ethanol"

all the regular maintenance has been done on the truck. i changed my brake pads because i had an abs sensor failing and the pads were cracked all over. they still had tons of meat left. friend of mine pulls a camper with his 8.1 truck and he just replaced the pads with 251K on the clock. he does a lot of highway driving, but still.
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6.23@109.71 pump gas. all motor.
05 2500hd. 6.0L
88 iroc-z 6.0L
one hauls, one hauls a$$.
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Old 12-29-2010, 10:13 AM   #10
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!! my 8.1L burb eats pads like crazy... about 20K miles they are gone.. granted is 8200lbs and im a bad driver so my wife says...
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Old 12-29-2010, 10:13 AM
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