1999 Sierra Wont go over 2k RPM

[daytonb]

Hey guys,

I own a 1999 GMC Sierra 2500 SLE with 135k miles. Recently the battery went bad and I had to replace it. Ever since replacing the battery I will randomly not be able to go past 2k RPMs and will bog down on hills. After leaving it for a few days it seemed to run fine and got well into the 5k RPM however the next day the problem came back.

There is no check engine light and it starts up immediately. I am unsure if it is a fuel filter/pump or something more serious.

As a note, I added a Flowmaster exhaust on it 4 months ago with no problems. I also checked the fuel pump fuses and all seemed to be O.K.

Any help would be greatly appreciated as I dont want to take it to a shop and get the run around.

 

[98trck]

My first thought is a clogged Catalytic converter
But I think that would be all the time limited rpm

 

[98trck]

Here is a shot in the dark
Gas tank vent system not working
Next time it does it take the gas cap
off for a moment

 

[daytonb]

Unfortunately, I just went and checked, while there was a little pressure released when I took off the gas cap the problem did not go away.

It will get up to 2k RPM and shift through gears at 2k. However, if I attempt to push it over 2k RPMS it bogs down to 1.5k and struggles. Going up small hills it will have a very difficult time.

 

[98trck]

have you taken your truck to a local auto parts store and have them scan it?
I have seen pending diagnostic codes when scanned that don't produce an SES light

 

[daytonb]

So I havent taken it anywhere to be tested, however I do own a OBD II sensor and no codes came up. I checked the cats with a thermal temperature gauge and they seemed to be working good, being 100 degrees hotter at the outfeed. I'm guessing it might be a bad fuel filter/ fuel pump.

 

[98trck]

is that the correct temperature pattern for a cat'd exhaust system
use the temperature gauge on a vehicle that is running good to compare temp readings to your truck
PETE