Ok guys I have a weird problem that, so far, has costed me $2400 and it still isn't fixed.

Info:
'98 Blazer LT, 154k miles, 4L60E trans, 4x4, 4dr

A couple weeks ago I had noticed a rattling coming from the catalytic converter which made me believe the catalyst was starting to break up, however the check engine light didn't come on and there were no stored codes, so I wasn't sure if the catalyst had broken up or a heat shield had just come loose.

Well, it continued running fine for a while with the rattling then one day it just seemed to have no power. Like, I would go to take off and it would not want to accelerate at an appreciable rate. If I floored it though, it would rev up to 4k+rpm and still not want to accelerate any faster. Also, my gas mileage was sucking terribly (figure a quarter to half a tank a day just for around town driving).

The symptoms made me think it was a transmission problem, so I put it in a transmission shop and they did $2400 worth of repairs. They said they rebuilt it, replaced an EPC solenoid, new sun shell, new pump, new torque converter, and I had them install a shift kit and corvette servo since I had been wanting that for a while.

I got it back yesterday and, well, it's still having the same problem. I've noticed when I do gas it hard and it revs up there is a new noise coming from the engine, sounds kinda like air escaping?

So my question is, is this typical of the catalytic converter going bad and severely clogging the exhaust, or is it most likely still a transmission problem? If its the exhaust being clogged I want to get it to an exhaust shop asap but if it's not I'm going to take it back to the transmission shop and have them do a more thorough diagnostic of it.

Thanks for reading if you read the whole thing, it is kinda long.

 

I think I would have done the exhaust shop first because the symptoms sound like a plugged cat (and it would have been cheaper ). Normally, you would not be able to hear the cat's broken insides rattle while driving, but when you rapped on it from beneath. You can remove the 02 sensor just ahead of the cat (it will be loud) and if the performance returns, then the cat is plugged.

 

and to throw in my experience, a clogged or broken cat wont always throw a code. the one in my brother's 98 ram had broken and turned sideways. it had no power and was very quiet, but no cat efficiency codes

 

Yeah, I would think your cat has gone bad and the rattle is probably the heat shield.

 

it could be that the cat broke apart inside and turned sideways, but i doubt you would be able to hear it while driving.

 

Sounds like a vacum leak try changing the plentum gasket leme know if that helped.