No power, no throttle response

[Dave-TransAm]

About two days ago I was driving home from work and noticed my car was being pretty sluggish. Now I notice I can give it full throttle in second gear (or any gear really) and I'll barely be moving at all, and the throttle response is worse than ever. Also, when I accelerate there is a loud hissing noise that I have never heard before. Anyone have any ideas of what these problems could be caused by? Thanks!

[Smittro]

Do you still have your factory cat on it?

Mine did exactly that too when the cat died.

Could be a Vac leak also.

[Dave-TransAm]

Yes it is still the stock cat. My check engine light is on and I had the code checked and they said it was the cat so it would probably be a good idea to replace it huh? Haha. But the dumbass who had the car before me put a custom catback on it and for some reason he thought it would be a good idea to weld it to the cat. When I replace it though, should I just get a new reproduction of the stock cat or just get a high flow cat? And I'll also check the vac for leaks.

[Smittro]

Yes it is still the stock cat. My check engine light is on and I had the code checked and they said it was the cat so it would probably be a good idea to replace it huh? Haha. But the dumbass who had the car before me put a custom catback on it and for some reason he thought it would be a good idea to weld it to the cat. When I replace it though, should I just get a new reproduction of the stock cat or just get a high flow cat? And I'll also check the vac for leaks.

I would get the high flow cat, because the reproduction or "direct fit" won't last and won't match the original diameter of the stock collector pipe.

Stock collector is 3" and the so called "direct fit" is only 2.5"..

If you don't have the code cleared it will go out on its own after a few run cycles once the cat is replaced.

You also don't have very many VAC lines, so if you're leaking from there it would throw a MAP code right away.

A manifold VAC leak will code quickly as well.

Prolly just your rear 02 causing the (efficiency) code because the cat is bad.

[Too Fast]

I would get the high flow cat, because the reproduction or "direct fit" won't last and won't match the original diameter of the stock collector pipe.

Stock collector is 3" and the so called "direct fit" is only 2.5"..

If you don't have the code cleared it will go out on its own after a few run cycles once the cat is replaced.

You also don't have very many VAC lines, so if you're leaking from there it would throw a MAP code right away.

A manifold VAC leak will code quickly as well.

Prolly just your rear 02 causing the (efficiency) code because the cat is bad.

Correct, but the rear O2 isn't necessarily bad. OP may not know that the PCM proves the O2 sensors before it will test for cat efficiency.

[Smittro]

Correct, but the rear O2 isn't necessarily bad. OP may not know that the PCM proves the O2 sensors before it will test for cat efficiency.

I know I'm correct.. I never said the 02 was bad.

Please reread the post. The rear 02 causes the code when the cat is bad, that does NOT mean the 02 is bad.

BTW V6 f-bodies only have one rear 02.

[Smittro]

Even if the rear 02 was bad, it would not effect performance nor cause a lack of power.

[Too Fast]

I know, Steve, I know, and I know you know. But the OP may be confused, I just wanted them or whoever else reads this thread to not be confused. As you know, not everyone here has the technical understanding you and I do. Your post #4 on this thread could be a bit confusing.

[Smittro]

Yeah you're right Steve, post #6 did'nt quite come out the way I meant it too either..

[Dave-TransAm]

I have the car over at my buddies house; his dad was a GM Mechanic for 40+ years and has worked on his fair share of fbodies so im sure we will be able to figure it out. I appreciate all the quick replies! Also if you guys have any more info it would still help

[Too Fast]

Well, more info for a problem like this could mean a lack of fuel or fuel pressure, or a dirty MAF. But since you said you hear the loud hissing, probably under any type of engine load, the first thing I'd eliminate would be a clogged converter(s).

[Dave-TransAm]

Just got quoted $650 for a new converter! Looked on Summit Racing and I can get a magnaflow hi-flow cat for $250 or somewhere around that price. Just so I can actually drive it, what do you guys think about cutting the exhaust off and rolling like that until the catalytic converter arrives and I can re-do the exhaust? And the reason I say cut it off is because the dumbass who owned it before me did a "custom" exhaust and welded it to the cat...

[Smittro]

Just got quoted $650 for a new converter! Looked on Summit Racing and I can get a magnaflow hi-flow cat for $250 or somewhere around that price. Just so I can actually drive it, what do you guys think about cutting the exhaust off and rolling like that until the catalytic converter arrives and I can re-do the exhaust? And the reason I say cut it off is because the dumbass who owned it before me did a "custom" exhaust and welded it to the cat...

I ran catless for a while myself but I added in a piece of strait pipe till the cat came in.

It will be crazy loud open collector..

I would'nt run open collector because of the flame issue, and the wire hardness for the rear 02 is right there.

[Too Fast]

Dave, follow above advice.