This may be of help:
From
http://www.w126.com -
"Engine
The engines are known for their durability. If an engine is properly maintained, it can easily run for 300.000 - 400.000 kilometers without a rebuild. The V8 engines are alloy engines and the walls of the cylinder housings are coated with a silicium-based layer. Expect to change a distribution chain every 250.000 kilometers. The early Bosch K-jetronic continuous fuel injection systems can develop a rough idle over time. Typically, a V8 should run about 650 - 700 rpm at idle when hot. If the car will develop a jumpy idle (jumping from about 1500 rpm to 500 and up again), the electronic control module is likely to be at fault. Post-1985 models were equipped with Bosch KE-jetronic pulsed fuel injection systems with a completely electronic engine management system. "
Hope this will help you.
