Shoot some starter fluid into the throttle body...if it starts for longer than usual then dies its fuel related if not either spark or a vacuum leak. Replace the idle control hoses if they are rock hard.
Those tests should help route you to the right place before spending money.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k