Had the following work done in the past 5 weeks and nothing else in the previous 6 months. It should be worth mentioning that the vehicle ran with a smooth idle prior to the first condition (# 1 described below) when vehicle did not start anymore. Chronology - Condition # 1 – (The vehicle will not start). Symptom is that of turning key with strong battery and cranking away, just not starting. Mobile mechanic replaced 7 spark plugs where most of the 8 plugs were oil soaked and he replaced both V-8 valve cover gaskets. This allowed the car to start but the nasty rough idle saga begins. He then went on to replace the PCV valve, Air Intake Idle valve and the fuel filter. This did not correct the rough idle symptom. I was not comfortable with his work so I sent him away and paid him about half of what he was asking for. Condition # 2 – (Rough Idling) – Since the first mechanic could not get the 8th plug out, I had a second mechanic come over to get it out with no problem. He also found one of the 8 coils was not correctly placed back on the plug. Rough Idle Problem persisted. Condition # 3 – 02 Oxygen Sensors – The CanOBD2 reader indicated that 02 Oxygen Sensors was lean or something but not the exact one of four so we changed all four (upstream/downstream). Rough Idle Problem persisted. Condition # 4 – Rough Idle Continued (currently idles at 700rpm roughly, runs smoother if I put it in neutral and gun it to 1000rpm), does not shut off, solid Check Engine light on dash. The CanOBD2 reader indicated possible vacuum leak. Will check those next.