I was out running around yesterday and noticed that my truck was slowly losing power and that my exhaust had gotten extremely quiet. I have headers and flowmaster and couldn't hardly hear it with my windows down. By the time I got home it would do about 15mph and barely made it up the small hill to my place. Now it won't start! I can smell fuel something terrible too. Any suggestions? It's a 360 magnum by the way...

 

Clogged cat.

 

Do you still have your CAT in the exhaust, if so it sounds like it may be plugged.

 

that was my first guess but it's not building up heat as if it's clogged...

 

now i got it to start and it shot me a code P0500 which is vehicle speed sensor malfunction. That's on the tranny though. Any idea what would cause that? I never tried to drive it, just started it

 

still sounds like a clogged cat.... punch that baby out and you won't have to worry about a quiet truck again

 

i'd love to punch it out but i don't want that 'downstream 02 sensor rich' code stuck on. Besides, it's been proven on different dyno tests that you actually lose power because the shape of the cat 'captures' the exhaust in a trap instead of it flowing straight through.

 

to solve the downstream o2 just put a couple spark plug arrestors on your o2 and put it back in. I can't see how gutting a CAT is worse for power than having an original.

 

meh, I'll take loud and obnoxious over a couple tenths in a quarter mile anyday..... I can't hear a (possible) tiny amount of power loss over the sound of my truck roarin down the road anyway

and dodgeboy's correct. Check the DIY links for the O2 trickery

 

if your exhaust was still loud i'd say you might be dragging a brake or binding up somewhere.

but since you now have a superquiet muffler, i'm agreeing with clogged cat.
to prove it, you can temporarily remove the front 02 sensor to see if some of your rpm's and power return,