| "Me Too" Often I neeed to start twice on a cold start, the engine won't crank past 800, you must turn off then the second start is fine, then any idling will sound like an idling harley until the engine gets up to temperature.
The problem is open-loop vs closed-loop mode. Most car egnine computers rely on the precise data of the oxygen sensors. However, oxygen sensors only work at high temperature ranges; that is, once the engine has reached normal operating temperature. Until that temperature is reached and the engine is warmed up, the engine controller runs the engine in open-loop mode. It's more like blindly mixing chemicals; x amoung of this + y amount of that and you should get z, but until the engine is warmed up can you remove the blindfold and instead ajust the amounts by monitoring the output. So when you change what the computer is expecting in ingredient x, it doesn't realize it and the output changes without it knowing. The only thing it does know is that the engine has slowed down to near-stall so it quickly overdoeses on x. The stumbling/harleying is this procedure repeating itself. A software fix could be for example extending that overdose period to something not so quick, or running the engine at 1250 rpm instead of trying to idle at 1000. Of course, those waste gas and produce more unmonitored emissions; the computer can't monitor emissions until all of those oxygen sensors are at operating temperature. And of course the government makes sure the emissions take precidence. | 
