Hello I'm a new comer to this site and have been reading some of your topics. It seems that you have alot of knowledge to the new trucks, so maybe you can help with mine. I have a 2005 GMC Sierra Ex. cab 5.3, 3:73 rear end. I have installed all the bolt ons that I can without the supercharger. I'm having a problem with loss of power. I was able to light up my 20" tires from first gear into second when I installed my JBA headers. One day I was racing and SS and redlined the motor. The motor shut down on me after 6100 rpms, and made a loud sqeal. It still seems to run ok, luckly, but it will not do a burn out now. I took to the dealer and they said no codes came up, so everythings fine. Wrong answer. So i took it a engine builder and tuner. They did everything they could to try and fix it, but they also could not find the problem. They adjusted the fuel and torque management, and said that something seems restricted. Can a new truck get clogged cats this early or my flowmaster breakdown inside? We thought of everything including a bent rod, but no signs of smoke coming out of the exhaust or a fouled plug. Could it be something in the comuter somewhere? A sensor? Does anyone know how to fix this?

 

first off welcome to the site, second I'm going to move this to a section where you'll get more feedback from your problem. Hope we can help you out!

 

My 99 is doing the same thing. Just put new fuel filter, tr-5 plugs, front 2 O2's, k&n drop in, and a flowmaster just dumped no tailpipe. When I get on it it wants to pull but just kinda stumbles through the rpm 's. Not trying to hi-jack, just baffled like you are. I was thinking maybe the cats are stopped up but I'm not sure. It's got almost 100k on it.

 

Mine is a 05 though, with 26,000 and use nothing but 92 octane. I'm baffled, nobody seems to know what is wrong with it. Some people think I'm crazy. The manager at the dealer drove in it with me, and got on it, it stills pulls real hard, but doesn't do the burn out, He said, are you sure something is wrong, because this thing will beat his 05' Denali. Nobody seems to believe what kind of burn out my truck use to do.

 

I've seen cats clogged as soon as 20k miles so it's worth a try.Easy to tell just a simple heat range check.

 

How do you do a heat range check?

 

How do like the borla exhaust? My Flowmaster just isn't loud enough. I heard an SS the other day and it sounded awsome. I'm wondering if he use an X pipe. Because it was very deep. It randles the windows in my house.

 

Today, my power came back again. So I lit up the tires to make sure it was back. Nice 30ft. patch. The temp was 92 in Vegas. Not quite sure what is causing this. Example: When its at its best, the throttle will be very touchy and want move with no problem, and will pull itself. When the loss of power occurs, I have to put the pedal down half way to get it moving. Its kind of like when you are driving with the wind at your back, and your ride is easy to move, but other times, its like going against the wind and no power. Can it be something in my electronic throttle? Or a dirty sensor somewhere?

 

The easy way to check your cats is when the truck is acting up, unscrew the front o2 sensors from both sides, leave them plugged in just hanging there. That will open up enough flow to let the motor act normal. If it fixes it then its the cats. Also low fuel pressure can act just like cats clogged up. Good luck.

 

I had my cats checked at one point.The exhaust shop simple put it on a lift let it run for about 5 mins before hand...but just used a lasor pointer type of thermometer.I'm sure you have seen one before.Just point ans shot and it gives you the temp.They point it directly in front of the cat and directly after it.If there is a big decrease in heat then there clogged if not there fine.When he checked mine they were like 490 degrees at the front and like 487 in the back.Those numbers are not exact but you get the idea....i can't remember if they were in the 490's or 480's but ethier way it was only a 3-5 degree drop.