Blocked precat and cat, poor performance *solved

[sjacoby]

I recently cut out my blocked pre-cat and temporarily clamped a flexible exhaust pipe in place of it. It was leaking pretty bad, so today a muffler shop welded a piece of pipe in place. It is very quiet but is running like it was before with a plugged pre-cat. Does it take time for the computer to learn the new exhaust in absence of the leak? What do I do to make it run smooth again. It will not accelarate or shift on the highway

[HenryJ]

Did it start running worse once you sealed up the exhaust leaks? Did the main cat plug up now too?

[hootz]

Sounds like you still have an exhaust restriction. An easy way to check for a restricted exhaust is to use a vacuum gauge. Find a vacuum port that has full vacuum at idle (some ports are ported and the vacuum increases as the rpm increases). With the engine idling in park, observe the vacuum gauge reading. I would expect about 17 inches of vacuum (give or take a few inches) at idle in park. Increase the rpm to about 2,500 and watch the gauge. Normally you would expect the gauge to stay the same or maybe increase a little with the transmission in park. If the gauge falls significantly when the rpm is increased you most likely have a severly restricted exhaust.

[riceburnr2005]

maybe whatever was in you're precat fell back into the main??

[sjacoby]

Thanks for your responses, ya turns out it was the main cat as well, replaced that at a muffler shop and they didn't require me to put in a new Y pipe and pre cat thank god. Runs like a dream now, forgot the power that I once had.
Thanks again

[HenryJ]

Glad it is back to normal.

[riceburnr2005]

that's what we're here for!!