BMW Repair: E46 engine shaking when idle, software compatibility issues, 2002 bmw 325ci

Question
Background Info: My 2002 BMW 325ci has a manual transmission and 43K miles. None of the indicator & warning lamps on the instrument cluster is currently on. I followed closely to BMW’s maintenance schedule. Inspection I Service was done on April 2006 at 38K miles. The front brakes were replaced. Coolant flush was performed. According to the service indicator, upcoming oil service is due in >9K miles.

Problem: Since two weeks ago, when the car is in idle, like I am at a red light or stop sign, there is a shaking that seems to me is coming from the engine. Someone suggested that might be a result of engine overheating. I do not believe that’s the case because the phenomenon exists even when I cold start the engine in the morning (I doubt if an overheat engine causes shaking anyway). The shaking is not very consistently: sometimes it’s more violent than other times. Sometimes it’s not shaking at all. When it does shake, the shaking will start to go away when the car is accelerated until it hits another stop and is put in neutral.

Another someone suggested that filling the gas tank with a bottle of over-the-counter fuel injector cleaner (like Chevron's Techron) and let the car run for couple tanks of gas the phenomenon may disappear. I need some advise from an expert. Thanks a bunch!


Answer
Susan, I smile when I see women driving manuals. Using Chevrons Techron in your Next two tanks of fuel is actually a great idea. BMW now endorses the product with re-labeling the bottle with a BMW badge and selling it as "BMW fuel system cleaner." Stuff works great if carbon build up on the intake valves is the source of the rough idle which it very well may be. If that doesn't work I would get to the dealer and request an engine computer (DME) software reprogramming. BMW is always implementing new software for software compatibility issues. Test drive with the Technician or Shopforeman to show him what the issue is (not the service advisor). Make sure you are using 91 octane gas or higher from a reputable station.
-Evan