My '84 DL40 has the 4-cylinder B21F engine with, I believe, the LH-Jetronic II fuel injection system.

It has always cranked without difficulty, and continues to crank easily, whether cold or warm. When cold, for the first thirty seconds after cranking, it runs rough and rich (black exhaust) with poor power. After I travel 1/2 block, the problem clears up and the engine runs smoothly, mostly.

The exception to this is at one intersection on my way home from work, I usually have to idle through several changes of the stop light. When I finally get the green, while accelerating the engine will often misfire. When it does this it seems to cut out momentarily, then it picks up again and all is well until the next morning, when the drill begins again.

One more symptom: for years I got about 25mpg in town, now mileage is down to 20-22mpg. I have removed and cleaned the injectors and poured several bottles of injector cleaner into the tank without changing the symptoms.

My favorite shop has not been able to correct the problem. Their diagnosis is carbon buildup in the intake tract. They say the carbon absorbs fuel for the first few seconds, causing the engine to run *lean*. I can't reconcile this with my observation of the sooty exhaust.