The little clips that hold all of your vehicle’s wires together aren’t perfect – far from it. They do get loose sometimes, and you should inspect the car at the first sign of trouble. The good news is that it’s usually pretty easy to plug it back in again.
One customer we had had their choke wire come off without their knowing. The choke is a plate the covers the air intake in your carburetor when you first start the car. It gives your engine a big bunch of gas to start the car, then eases off for a normal running mixture of air and gas.
Our customer kept pumping the gas, since the car was running rough, which flooded the engine with too much gas. Eventually, so much gas was in their engine, it leaked into the oil system, ruined the oil, and fouled up the spark plugs.
Once the problem was discovered it took three oil changes to remove all the gas from the engine and two sets of sparks plugs before the bug ran correctly.