Can't tow

[burgundyz71]

My buddy has a 97 GMC 5.7 that seems to run fine but as soon as he hooks into his camper, weighing around 3700 lbs it bucks and shakes and has a hard time holding 30mph on a hill that usually you wouldn't even notice. He tried the fuel filter and didn't seem to do any good. Could a plugged up cat cause this or any other thoughts you guys/gals may have ?

[Metz Motorsports]

My brother ran into the same type of thing with his '90 Chevy. The truck ran fine until we hooked a trailer (4500 pounds) to it and drove it to Seattle (about 280 miles). Ran fine going over, but on the way back it started buckin and snortin', loosin power and the gas milage plummeted. Got home and unhooked the trailer and it was fine. Ended up being the CAT was shot. Hope this helps.

 

-Jason

[tahoe33]

My brother ran into the same type of thing with his '90 Chevy.  The truck ran fine until we hooked a trailer (4500 pounds) to it and drove it to Seattle (about 280 miles).  Ran fine going over, but on the way back it started buckin and snortin', loosin power and the gas milage plummeted.  Got home and unhooked the trailer and it was fine.  Ended up being the CAT was shot.  Hope this helps.

 

-Jason

 

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[tahoe33]

I have a 1995 Tahoe and had the same problem with it not towing my trailer. I test the cat converter with the the pressure gauge that screws into the oxygen sensor location and it tested ok. I changed the cat converter and now the truck pulls the trailer with no problem. The gas milage went from 13 mpg to 15.5 mpg around town and 17.5 on the highway. The cat converter cost $250. I would change it first.