Viper588

Hey guys i need to replace the passenger side cat on my 92. Ive gotten all of the nuts off except for one of the flange nuts where the cat bolts to the manifold. One of the nuts is almost directly above the exhaust pipe and i cant figure any way to get a socket or wrench on it with room to turn it. The only solution i can come up with it to just cut the old pipe which would allow me to access the nut, though id have the same issue when reinstalling, and i would be replacing it anyway though i normally dont like to cut the old parts up if possible. Anyone ever done it and have some sort of trick or advise for getting to the last nut?... Also one of the studs broke off which i was told by someone is fairly common when replacing the cat, im assuming i will have to just drill it out and either use an extractor or tap it for a larger stud but any advise on that would be welcomed as well. Thanks!

Silver96ce

As I recollect when I pulled mine off - I think I used a wobble extension and a Gearwrench mid-length socket on the difficult to access stud. Can't remember if I used 1/4 or 3/8 drive however. Also I sprayed it down with PBblaster beforehand.

I broke one too and felt it best to remove the passenger manifold and drill it out on the bench. I center punched it, started with a small cobalt bit and used progressively larger drill bits until I got pretty close to the original threads. Then I used a 10-1.50 metric tap (IIRC) to clean out the threads. I believe I got the new studs at NAPA (again should be 10-1.50 metric) and I replaced all three. Don't forget the cutting oil when drilling and tapping.
When I reinstalled the manifold I used the GM gasket.
Good luck.

Viper588

Well i took the old one off today and it was a pain to do. I ended up having to cut it unfortunately but removed the manifold as well in order to drill out that stud. Looking at the new one i purchased to put on im not sure how much i like it, MUCH smaller cat and it has some sort of bracket that the old one does not have on it so im not sure how confident i am about ti fitting correctly. The only issue i ran into was that i broke a sensor on the block between the rear runners of the manifold. When i first tugged on the manifold it slipped and landed on that sensor and snapped it in two. Does anyone know which sensor that is so i can replace it? Thanks!

Silver96ce

That should be one of the two engine coolant temperature sensors - that one I believe runs the analog gauge in the dash.

don hall

The '92 has two O2 sensors. Verify the sensor you removed is an O2 sensor:

http://tech.corvettecentral.com/2007...oxygen-sensor/

don hall

Assuming it is a '96 vette....the digital temp sensor is located on the water pump. The analog sensor/sender is located in the block between cyl
6 & 8.

If removing the cat, the O2 sensor would be the only sensor involved. At 83, my memory is suspect.

Viper588

Ok guys have an update, you guys were correct the sensor i broke was the coolant temp sensor for the analog gauge on the dash! I replaced the cat and O2 while i was doing since i was there. Everything went fine but i had a misfire once I started the car after, found that to be one of the injectors. This was the 3rd injector thats gone bad in the last 6 months which i thought was odd but theres an issue now. At idle and while driving there is a "whistle" noise coming from the exhaust. At first i though i didn't tighten a clamp enough but its coming from the rear of the exhaust/muffler area. Also under hard acceleration the car will just stop/hesitate and then continue accelerating. Im thinking there might be a piece of the cat(which was in pieces when i took a look inside) lodged in the exhaust or muffler somewhere. What do you guys think? Also could the blockage cause the acceleration issue?

Silver96ce

Could the whistle be part of the old cat? Maybe. Do you still have the old cat? If you do take a look inside and see how much is missing. If a lot is missing, try the hand over the exhaust outlet test. With the engine running, put one hand with rag over the drivers side and gauge how much pressure you get as opposed to the passenger side. If the passenger side is much less - then you have a good chance of some type of blockage. If there is a blockage, hopefully it's in the muffler. Maybe you can take it to a muffler shop, cut the pipe before the muffler and shake it out then have it welded back on. If not replacement mufflers are available from many vendors.

As for the injectors, I got some used Bosch III from FIC and replaced mine a few years ago. They are still running fine and a lot of guys on here have used them with great success and the price is right. Here's a link -

http://www.fuelinjectorconnection.co...gory&cat_id=68

As to your acceleration problem - it could be related to the cat but I doubt it since it seems to be more of a "hiccup" rather than a inability to accelerate past a certain point. It could be fuel related or ignition related. If you have a fuel pressure tester hook it up and see you what you have. Turn the ignition on but don't start the engine. As best as I found quickly looking in the '96 FSM it should be around 41-47 PSI. Running at idle it should be 3-10 PSI less.

Also pull the vacuum hose off the Fuel Pressure Regulator. See if there is any fuel in it or if there is a strong fuel smell. If so, the regulator is bad.

Unfortunately the acceleration problem could also be the opti. I had a problem that was much like that without a code being set and it was the opti last year.

If you don't already have it, get a copy of the FSM. It has absolutely invaluable diagnostic charts for problems like these. Check Ebay for paper and CD versions. I have the CD version for the '96 year and have gotten used to it over the last few years.

Post back with what you find. Good luck.

Viper588

So i went out this morning expecting to pull the exhaust to check for the pieces and the whistling noise is gone, acceleration issue is gone and i dont hear any rattles like i did last night. Im trying to decide whether i should still pull it and check for peace of mind or if i should wait to see if/when the issue returns and tackle it at that point since it looks like pulling the exhaust is a pain without a lift.

I do have the old cat and it is completely destroyed inside, just a few chucks rolling around. I did put my hand over the exhaust least night and there was a noticeable difference between the two sides.

I wish i new about those injectors a few months back =P i may have to pick up a set and swap them all out since it seems like the originals are starting to go, thanks!

I check fuel pressure a few weeks ago trying to track down a weird starting issue, with car off it hit 45psi and settled to 40psi and held for quite a while, i did not check at idle. The opti was replaced maybe 6 years ago but only has about 20k miles on it since then. Still a possibility though. I also checked vacuum yesterday and its holding 20.5-21.

i still have to pick up a FSM, i looked awhile back but never picked one up.

I appreciate all the responses and advice!

Silver96ce

Good to hear the problems are gone. At this point I would take a wait and see approach like you are thinking.

Enjoy the car and have a great Memorial Day Weekend!