If that's all he he did, then he didn't "diagnose" it properly.
With a hard start condition and the black smoke and the check engine light on, he should first retrieve the trouble codes. What were the codes stored in memory?
Next, hook up a scanner with "live data" capabilities. Turn the key on, and look at the coolant temperature. If the car is "overnight cold", the coolant temp should be close to the outside air temperature. If it is a significantly colder reading, that could cause the black smoke.
Next, start the car and watch the readings from the mass air flow sensor and the coolant temperature sensor. Are they normal readings?
If these check out ok, let us know and I'll give you more things to check out next.
Last edited by 2001Jettagls; 12-23-2012 at 02:53 PM.