When I clean and regap the spark plugs on my 1976 BMW 2002, I have noticed how the #1 and #4 plugs always have a white crust-like deposit on both electrodes and insulator, in contrast to #2 and #3, which show dark gray-colored electrodes and very little deposit. Although I’m not an expert in combustion engineering, this observation led me to believe that the four cylinders are not getting the same gas-air mixture concentration.

Three questions come to mind:

1. Did the engineers from Munich screw up when they designed the inlet manifold system?
2. Can I do anything to improve the uniformity of the gas-air mixture?
3. Will this imbalance cause a more serious problem in the long run?

Except for slight stumbling and a hint of backfiring when getting underway with a cold engine, the car is in excellent running condition. I’m interested to know whether this problem is peculiar to my car or is indeed design-related and common to other 2002

Aldo Magri Tech. Ed. Note: You don’t need to be an expert in combustion engineering to see that the inlet tubes on all carbureted slant-configuration engines are of different lengths. In a life span of 100,000 miles without major tear-down this will make no difference at all.