Help!!
I've got a '91 Firebird. 305 TBI/th700.
It has been losing power steadily over the last week. It's to the point now where it'll barely maintain highway speed.
It idles normally and has normal torque (for a 305 ) below 2,000 RPM but develops no power above this.
It behaves as if it can't breathe, has a severe exhaust restriction, or severely retarded timing. Maybe insufficient fuel flow? I don't hear a knock, but the ALDL set a 43 fault code. All gauges register normal.
The exhaust is waay too quiet, the pulses feel weak and hot. When I push the accelerator at highway speed, the intake gets loud like it's lugging, but nothing from the exhaust (save a hissing noise I might just be imagining).
My first thought was that the cat disintegrated, but I don't hear any palladium rattling around in there.
So whaddya think? Plugged cat? Fuel filter? Something else?
I gotta get this pig back up to speed. Any help is appreciated!
-John

 

I agree, most likely a cat. When the converter on my sisters Firebird plugged up, it made no audible sound. Once removed, a solid chunk nearly about the size of a orange broke off and turned 90*, blocking all flow.

It wouldn't hurt to replace the fuel filter either.

 

I decided to tackle the fuel filter first. Heckuva place to put it, btw (I'm shocked nobody ever came up with a relocation kit).
If that doesn't fix it, I'll try the cat next.
Thanks for the replies!
-John

 

Wasn't the fuel filter....although it was horribly clogged as well. Guess I'll check the cat next.
Anybody know what clamp I need for the front?

 

The car seems to be running better now that I changed the filter, but it's not at full power. I reset the computer, but I don't know if the BLMs are stored in NVM. Does anybody know offhand?
If that's the case, I may just need to drive it awhile while it learns leaner settings.

 

It should reset to base settings and learn from there. It shouldn't take more than a couple of minutes before it settles in.

 

Anybody know offhand what size exhaust clamp is on the front of the cat? I'm gonna pull it.

 

Good luck. It is probably one of those ring style clamps. I believe it might be a 2 1/2 to 3 in.