TJ

iTrader: (10)

are you using GM pads? all the aftermarket replacements are junk. fade, wont stop, build heat and warp rotors, turn you wheels black.

i pull a small enclosed trailer everyday and i have never, ever had my wheels even with a hint of brake dunt on them.
GM pads are high as girrafe puzzy, but they dont make any noise either. i know a guy in parts, so i get employee pricing on them. if you know someone, or find a deal online, im sure you can get a similar price.


got a scanner hooked to the truck today. timing, map, maf, 02's all check out.
it did show that im using 50% throttle to accelerate like a normally would to get up to speed, which is too much IMO. getting up with the local tuner on friday night and he is going to hook a laptop up and check what he can.

hog

The HD trucks have the dual 3" cats IIRC, 8.1 or 6.0, they are the same.

peace
Hog

TJ

iTrader: (10)

so i cut 2 huge windows in the bottom of the muffler to see if my truck gained any power back. just got louder. still down on power.

to anyone that hasnt cut the stock muffler apart, they cant flow for ****.
there are 3 tubes in the front chamber, and then a wall, and then the last chamber only has one small tube, maybe 2 1/4 inch. there is no reason to have 3.5 inch pipes going in and a y pipe going into a single tailpipe with a muffler that has a tube this small.

when i cut the holes in the mufflers, the piping immediately behind the cats are 200 degrees hotter than the cats.

today after driving it 22 miles, the cats were 260-270, and behind them is 470 degrees.

are my cats clogged? i wont have time to get to a muffler shop for a week. i hate to cut my cats, but i also hate to hurt my motor too.

i have no clue to whats going on.
measured exhaust temp on a 6.0 van and it was only 350's in the muffler. same temps in the pipes and cats. so that would lead me to believe the cats are fine.

wasted the whole day now ive got a loud *** truck.

MikeGyver

iTrader: (5)

Everything adds up to that you are dumping a shitload of fuel into the exhaust in my opinion. No power, poor gas mileage, exhaust cool before the cats compared to the van. That's what cats do, burn what is unburnable in the engine, or and what wasn't burnt in the engine. It makes sense, the van has a higher pre-cat temp because the fuel is being burnt, and a lower post-cat temp because there is less combustion in the cat. Your post cat temperature is so high because of all the fuel that is being combusted by catalytic action.
That's my $0.02.

MikeGyver

iTrader: (5)

Of course now that I think about it, too lean would make more sense, if the mixture is too lean to burn in the engine, but the cats can burn it.

Either way, I'm presenting fuel mixture as a possibility. I think if the ignition was super-retarded, like with bad knock sensors, the fuel would burn in the exhaust before the cats.

MikeGyver

iTrader: (5)

I'm glad to be so much help.

TJ

iTrader: (10)

thanks for the posts. i cut 2 huge holes in the muffler yesterday to no avail. truck is just loud now.
no block, no clog. pipe after cat is now 570 degrees, but the cats are still 270-280 on my gun. 300-310 in front of the cats.

i had something setup with the local tuner, but he cancelled on me.
im just going to let it blow up.

try to get up with my buddy at the dealer and see if he can let me borrow a tranny line pressure gauge.
only other thing i know to do is do a compression check or a leakdown on it.

StuDdERinGP

i dont know if you checked, but my fuel pump started pumping air. would run and pressure tested good, but was short on power like you are saying. only way to tell was to bleed fuel from the rail through a clear hose. replaced pump and all is well.

TJ

iTrader: (10)

im not enabled enough to answer that question.

took it to my buddy at the dealer today and hooked it up to a GM tech II machine and everything looked pretty good. the ecm is adding 8% fuel at certain times, but he said that was in the parameters or running normal. he said 10% plus would throw a code.
put in an exhuast pressure gauge and all is well. exhaust is not a resriction, cats are good.
# 6 had some stored misfires, but nothing that has thrown a code. he let it idled, loaded the converter up real hard on the brakes and checked some fuel things and transmission stuff and all was good. took it for a drive and all was fine. couldnt get the #6 to show a misfire, so not really an issue he said.
it runs like a dog and is getting worse today. trailer felt like it was loaded to the max and im pulling empty. also checked with another friend of mine thats a GM tech and he said cats as well.

when racing starts up, i seriously doubt its going to drag my 24ft loaded with any kind of speed. if it wont pull a empty 6x14 i know its going to struggle with more weight.

2manycars

iTrader: (7)

Sounds like compression check time.

Don't forget a new cap and rotor!