Um, wait. Hold on a second here. We're talking about an L36 that has 160,000 miles on an original UIM and LIM gaskets?

Unless I've missed something completely, misfiring, stalling completely and smoke would tell me coolant in cylinders?

I mean, rotten egg, ok, sure, cat, but coolant in cylinders will kill an o2 which will kill a cat, makes sense to me.

I'm prettty sure they're prolly original. How would i test them out to see if they were shot?

thats why i told him to check his oil if he was leaking coolant internally it would show up in his oil , but he said it looked normal so...

and would they keep the car from running? because i thought the car would just run poorly but i could be wrong

thats osmething you dont test you just remove and replace and they are prone to fail

ok. Is that hard to do? I'm pretty sure it could use them. I bought the car used and it had a little over 110k when i bought it 4 year or so ago. Do you think this would make the car driveable again?

Symptoms of a bad cat:

Power drops off after the car warms up.
Loss of power at full throttle.
Rattling noise.
Higher operating temps.

Typically it will NOT cause stumbling at idle or low rpm'*.

If you suspect the cat, go to an exhaust shop, and have a backpressure test performed. Don't shotgun it based on guesses.

Keep a very close eye on your coolant.

And keep in mind 95% of the misfire problems will be plugs/wires. The other 5% will be split between coils or a fueling component.

well, the symptoms are all there, but now i have a problem of getting the car running. Would a cat make a car just stall out and die? It turns over but wont fire up

You mention it felt like the car ran on 3 cylinders. Part of the programming is when the car reaches a critical temperature the PCM stops firing 3 of the cylinders to reduce the amount of heat. At that point you are supposed to notice and pull over and have it towed to a shop to be fixed.

While most of your post could seem like a bad cat. You don't mention what color the smoke out the tailpipes was.. if it'* white.. that'* a good sign of coolant in the cylinders. While Buick had you check your oil which is a good first step.... that doesn't take into account that when an upper intake manifold (UIM) fails..it doesn't dump coolant into the oil. It dumps into the cylinders. (Air/fuel intake system).

Either way.. no matter what your current issue is, you should read and be aware of the upper intake issues. Here is a link to the information

http://www.bonnevilleclub.com/forum/...e=article&k=38

No. Check your oil and coolant immediately for level and/or mixing. Try cranking it, then pull the plugs and inspect them for coolant.

If you find any on any of the plugs, drain the oil immediately and let us know.