2000 Silverado Powerloss

[Ironmanstl]

I have a 2000 Chev Silverado 2500 with a 6.0 L.

For about 6 months now when I start the truck and pull away it takes about 30 seconds or so for it to have normal power. Until then it is very doggish and underpowered, then all of a sudden it will spring to life and pull away.

About that time I had a code for a hi and low voltage on one of my rear O2 sensors. I replaced the sensor, but the same codes still came back.

Recently I was coming home on a trip and the truck went into a limp mode is the best I can explain it. The motor would not rev above 2500 rpm, or downshift to an rpm above 2500.

 

New fuel pump and filter last year.

Coolant level is correct.

The transmission was flushed last year and shifts great all the time.

 

Do you think this may be a bad catalytic converter?

[theroot]

I think I may have the same thing happening....Only happens when it starts (pretty much when cold too but I dont think always), runs ok at 1/4 throttle but if u open anymore than that, cuts out completely and seems to shift into 4th until throttle is backed off. Ive been able to eliminate the problem one of two ways.... shut off engine and restart until gone...sometimes once but as many as 10.....or by blipping the throttle wide open on off and on for awhile, but dont like this option or the restart.

 

Im thinking somthing electrical but I really have no clue....other than that this has been a great truck, as have all of my past GMCs (3) btw mine is an 04 2500 (not HD) 4x4 slt cc 6.0L 4spd trannie (373 rr end) with about 40,000mi.

 

Hope im not ramblin too much....just tryin to give enough info....

 

thanks in advance..