Originally Posted by veryslowbenz
...and to answer your question: no, the county emissions test place doesn't adjust CO%. I haven't taken it to a shop, yet. I'm a vacuum system dummy--what are the obvious vac leak areas? Can you point me to a procedure to check the fuel pressure?
First, listen for anything that hisses. Odds are, the hissing sound is a vacuum leak.
Next, hook a volt meter up to one of your O2 sensors. Check to see that the voltage is switching between two different levels (usually around 0.1 volts at the low side and 0.9 volts at the high side). It should be going back and forth. The quicker it changes, the better the O2 sensor is.
Now, with the volt meter on the O2 sensor, spray a little bit of "throttle body cleaner" down the intake at the air flap (with the air cleaner removed). Watch what happens to the voltage at the O2 sensor. It should go up and stay at 0.9 volts or so. That's an indication that it's running really rich (the extra "fuel" from the cleaner spray).
Start spraying cleaner around the vacuum hoses, and especially around the base of the fuel injectors. Watch your volt meter and listen to the idle. If the volt meter shoots up to 0.9 volts and stays there or the idle speed increases when you spray cleaner on something, there's a leak at that point.
The O-rings at the injectors are a notorious leak spot. Vacuum hoses get old and crack. The hard plastic vacuum lines (the really thin ones) get brittle and break. Intake manifold gaskets can also crack and start leaking on a car this old. You'd see that if you spray where the manifold and head meet.
Oh, and since you have a V8, you might have a left and right O2 sensor (I don't remember on these cars, and I don't have V8's in mine). If that's the case, hook the volt meter to the right bank O2 sensor when spraying the cleaner around the right side of the engine, and hook up to the left bank O2 sensor when spraying around the left side.