Here'* the sequence of events:

car is running fine night before, next morning my wife starts it up, it runs okay for a few minutes, then starts blowing tons of whitish smoke (hopefully not steam, but I"m not sure).
Car is parked until the next day and I start it with the white smoke again, but it goes away after warmup. It still runs terrible and is missing badly, check engine light, and a P0300 OBD code.
This happened before, but along with the P0300 code was an oxygen sensor code. I bought one but never replaced it since it was fine by the time I got the new one. I went ahead and installed it today, but it didn't help.
Sorry about the long post, here'* my question: Do I start replacing coil packs/wires/plugs? How do I diagnose a bad upper intake or head gasket?

You probably had a UIM failure, the coolant must have gotten in the motor in order to produce that much white smoke and the car will run badly which you reported so it sounds like a UIM failure since you have a 96 SE.

Check your coolant for proper level, and check your dipstick for evidence of water (coolant in it). Milky brown.

If you find that, drain your oil immediately. The L36 motor you have is notorious for eating upper intake manifolds and ingesting coolant.

Let us know what you find and we'll take it from there with you.

sounds like the UIM let go completely. You need to check the oil, and if it is high, watery or looks funny get it out of there ASAP!!!

P0300 is a random multiple misfire. Sounds like the UIM blew, coolant fouled all the plugs and now it is burning coolant AND misfiring.

IMO, you need to change your oil, take the UIM and LIM off and fix that ASAP, to prevent further engine damge.

DO NOT START THE CAR again.

this is not good. We just fixed the front end on this thing after an accident (see my prior posts), and were going to sell it. I agree that it is the UIM. I changed the coils and it didn't help. I noticed the coolant overflow res was a little low, and filled it. It immediately dropped again, and the oil appears to be higher.
Dont they make aftermarket UIM'* now?

You need to either get a Dorman or PM Bob Dillion for a sleeved UIM, but first you need to read this article, it'll have the part numbers for the parts you will need, a Dorman UIM, aluminum LIM gaskets.

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

laff, where are you located? there may be someone in the area that has swapped the UIM and LIM gaskets that would be willing to help you do it.

You need to not run the car anymore and change the oil ASAP. Having coolant in your oil is allowing a corossive material to eat away at your crank bearings.

Thanks to Boosty'* junkyard crawl, sleeved uppers are in stock. PM me for details.

I've had it off before, but just replaced the gasket, but I haven't done the lower on this car. I'll have to go look at it, but I'm curious if I'll have to pull the heads?
Now I'll have to figure out the PM thing...

PM = private message. There are little boxes below everyones post so that you can send them one. Your inbox link is at the top of the page between profile and log out

Be sure to replace the lower intake gaskets when you do this, they are known to go bad.