wierd sucking or venting noise

[HATNINJA]

Ok this is my first real post here. I have a 96 ssei 150000 miles on it. My wife drives it mostly, about three weeks ago she said it was missing and no power. I pulled codes and just the same evap code it always has. Well yesterday I finally drove it and it ran like a dog. This was the first time ive had a chance to look at it. Pulled codes this time there was mutiple random misfires. Popped the hood removed the cover and found the vacuum hose to the trans module disconnected reconnected it and she ran smooth. I took it for a test drive and the super charger sounds funny and not normal power. Boost at idle is -7 and it seems proper driving until I give it more gas it actually goes past 10 and the power dont seem right and it makes a real wierd noise like its venting boost air? Im stumped.

[willwren]

If it's at -7 at idle, you have another vacuum leak.

Try to find it. In addition, the red link in my signature contains some troubleshooting steps. Tell us what you find.

[HATNINJA]

Ok I cant find any vacuum leaks. Someone mentioned the catylitic converter sp. If I gut my converter will it give me codes?

[willwren]

Yes it will. And if your cat was plugged, you'd know it when driving, especially after warmup. It would have nearly no power, similar to missing on 2 or 3 cylinders. If you suspect the cat, get a backpressure test done on it by an exhaust shop. If it's bad, don't let them replace it, come back here first for more economical performance options.

Your car has two O2 sensors. The rear one is solely for sniffing the exhaust after the Cat. If you delete the cat or gut it, you'll throw codes to kingdom come AND you'll lose some low-end torque.

It is possible the Cat is the culprit based on the boost gauge, but not common. A vacuum leak is still the most likely culprit. Sometimes they can be VERY hard to find.

[HATNINJA]

I just got back from the shop and yes it is the cat. Now tell me about these economical options.

[willwren]

Can someone toss out some part numbers, sources, and prices for 2.5" high-flow cats with a rear O2?

(I don't use the same one you do, but many others here do)


Buying your own and paying a small fee to have it installed can be 300x cheaper than simply having an exhaust shop do the whole job. Most shops charge over $200 for a catalytic converter, you can get them in the 50-60 range usually, and that's a better-performing High-flow unit of name-brand manufacturing.