Volvo P220 B18 troubles

Driving on a highway I suddenly got a stuttering engine. It kept running but very irregular. After about 10 minutes the engine stabilized, although not did not run very smooth.

First thought was a problem with the fuel supply. Maybe there was some dirt coming from the tank. I did not take any action. Also because the engine runs smooth when cold.

After some time the stuttering came back when the engine was hot. So I decided to check the membrane of the Stromberg carburetor. And indeed, there happened to be a tear in the membrane. So I replaced it with a new one and thought the problem was solved.

Wrong. The stuttering came back when the engine was hot.

Next thing I tried was replacing the ignition coil as these sometimes go wrong when hot. Although there seemed to be some improvement, it vanished when the engine got hot.

Next try was replacing the distributor. This time I was successful! The engine now runs smooth, both cold and hot. So I wondered what was wrong with the old distributor. There were no visible irregularities. As the capacitor was replaced before I suspected the rotor. I used a multimeter to measure it's resistance: 5kOhm. I then warmed up the rotor and look: the resistance quickly rose to infinite!

Problem solved!