Hello! Welcome to Edmunds. I want to help you figure this out, but need much more information. First, what engine are you running? Has there been any work done to the engine lately? When this started, did it start suddenly, or was there a lead-in to it? When it is running, does it run smoothly or rough? Has anything electrical or electronic been added recently? When it dies is there a strong smell of gasoline, or no smell at all? Have you tried disconnecting the air-cleaner and see if the result is the same? You see, there are so many things that could cause this, without a plethora of information it is almost imposable to even guess at. Being a 93, it is OBDI equipped, this means to read trouble codes you need an OBDI meter or the know how to jump the reader terminals to make the check engine light flash the codes. Do you know someone who is good with early engines and the OBDI system who could help you collect some information about the condition? Oh, and when the engine is cold, does it crank hard before starting, or does it start right up? The answers to all these questions create a statement of what is going on with the mechanics of your engine, the sensors that collect information from it and the computer that interprets that information and makes constant adjustments to the engine as it runs. Ten to fifteen minutes is about long enough for the engine to reach full operating temperature at idle, and it sounds like something is happening when the system switches from closed loop to open loop idle, but again, I must have more info. Looking forward to your follow-up post. Sorry I couldn't be more helpful this time around.
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