Tip #3
K.I.S.S. The miss
Don't look for a complex solution to a simple problem. If you listen to and feel the exhaust pulses as they exit the tailpipes (don't grab the hot metal pipes), the engine will give you a good indication of where the problem is. If the exhaust has a dedicated misfire, then the problem is usually in one cylinder and may be ignition- or valvetrain-related, such as a broken valvespring. A fuel delivery problem will affect all cylinders and the exhaust will be uniformly choppy. If your Pontiac has true dual exhaust with no crossover or x-type pipe, a single cylinder miss can even be traced to its cylinder bank before you open the hood.
Tip #5
Vibration
All Pontiacs are subjected to vibration while traveling down the road, so check that the distributor and carburetor hold-down bolts haven't worked loose. The former will cause erratic timing and the latter, a vacuum leak and lean condition. Do the same for a crank trigger (if so equipped), or any other component that runs the engine. If you installed an aluminum intake recently, check the intake bolt and carb bolt torque again, as heat cycling of the engine could cause them to loosen, causing a vacuum leak, even if you torqued them correctly when you installed them. Spark plugs can sometimes loosen as well, due to vibration and heat cycling.
Tip #4
Get Connected
Any electrical circuit that interfaces with the ignition is susceptible to a loose or dirty connection that can cause poor engine performance. Start by checking the secondary wires on the distributor cap and spark plugs. Be sure that the connections are clean and tight, and that none of the wires are burned, dry rotted, or sliced. Also, visually inspect and grab the power and ground connections to the ignition box, tachometer, alternator, ignition switch, and battery. If the connection is in question, clean and tighten it and test the engine again.
Tip #6
Vacuum Leak
A vacuum leak can cause rough idling and poor part-throttle performance since unmetered air is entering the engine, resulting in a lean condition. The quick way to determine if you have a vacuum leak is to listen for a whistling sound at idle and part-throttle. Since not all of them whistle, another method is to cover the top of the carb with your hand while the engine is running. If the idle smoothes out, you have a vacuum leak; if the Pontiac stalls, you don't. A quick backyard way to trace the leak is to spray a mixture of dishwashing liquid and water (use the "stream" setting on a spray bottle or even use a kid's squirt gun) in areas where you think it may be (intake manifold at head flanges or base of the carb, etc.). When the idle smoothes out, you've found it. If you packed the vacuum gauge, stock engines produce 17-21 inches of vacuum normally, modifieds probably less.