Originally Posted by
David T
Vacuum leaks are the #1 cause for hunting (surging) at idle. But ANY imbalance among the cylinders can cause it. That means each injector, intake and exhaust valve, spark plug, etc, MUST be tuned as closely to each other as possible. On one car the reluctor gap inside the distributor was not equal on every point causing an imbalance. Often when you fix one thing it may make the hunting seem worse because now the motor has become more sensitive to other imbalances. The place to start is to check and adjust all of the valves and do a cylinder compression test. If you can't get all of the cylinders within 5% you will never get it to stop hunting.