Have a 99 420a car and it has me baffled. When you first start it (doesn't matter if the engine is hot, cold or somewhere in between) the engines idles and runs fine for about 20 to 30 seconds then it starts acting up. the idle speed drops and if you are trying to drive durring this it has no power and you have to keep messing with the throttle. Then for no reason after approx. 2 min. its like someone flips a switch and its fine. Any ideas? Thanks in advance!