find out which cylinder is the weakest, connect a vacuum gauge and
tachometer to the engine. Run the engine at normal operating temperature;
write down the indicator readings at idle. With the engine running
disconnect the number one spark plug wire from the distributor cap
(DANGER! take precautions to avoid being shocked). Once the plug
wire is removed, write down the readings of the indicators. Replace
the removed wire (DANGER! Take precautions to avoid being shocked).
Continue removing each wire one at a time, writing down the indicator
readings. Subtract each reading from the initial reading. The lowest
reading would indicate the weakest cylinder, indicating that the
cylinder is not contributing that much power.