Quote Originally Posted by Gman View Post
The fuel/air mix has a huge dependency on the temperature of the engine. The old-school analogy is the choke on a mechanical engine. You have to run a rich mixture when the engine is cold to start it. When the engine gets hot, the mix can be leaned out. The GM engines run as lean as possible to reduce the emissions that you're failing. When the thermostat is stuck open, the coolant flow is too high for the engine to get to its proper operating temperature. Replacing the thermostat reduces the water flow and allows the engine to get to full operating temperature and the computer will lean out the fuel/air mixture properly.
Okay, that makes sense. So, as it stands...tomorrow morning - I am going to:

1. Change the oil
2. New Air Filter
3. New Thermostat
4. De-carbon the throttle body to include the IAC valve & mass air-flow sensor
5. Drop some BG44K in the tank along with some decent gas (only on a 1/4 tank now anyway)
6. New plug wires

I agree with Gman and I pulled one of the plugs out of the car and it looked fine. My friend in Texas (also a master mech) said he agrees the NGK plugs are top shelf, but he also said if the car is starting easy, running smooth (not missing) he doesn't believe that changing them will be a big difference in regard to emissions. He did recommend new plug wires since it's going on 6 years. Also, since I only have to do emissions every 2 years, I only plan on running this little gem for about another year at the most. This is the first time it's ever given me any real issues. It's a great running car.