I just purchased a 1989 Formula 350 with 70,000 miles on it. When I took the car for a test drive it ran excellent. Over the weekend, the seller changed cap, rotor, fuel filter, o2 sensor and set the timing to 8deg BTDC and put a bottle of fuel injector cleaner in. The car ran fine when I drove it home but I did notice the idle surging. As i cut the wheels sharply coming into my driveway the car stalled and would not restart. After about 20min it restarted but when I gave it gas the car only sputtered but didn't move at all. I then waited a minute or so and restarted the car after shutting it off and it drove fine, but the surging idle problem was still there. Please help me out guys.

 

Id start by checking over the things he touched, like cap, rotor, the timing... Make sure all the connectors and vacuum lines are attached and not broken or damaged.

 

Here is an update. After the car sits over night I start it up and it runs great until I shut it off, wait 20min or so and try to restart it. It then has a surging idle and bogs down when I give it any gas. I am thinking it is a sensor but I don't know which one. Also, when I start the car after it has been sitting overnight the oil pressure gauge nearly pegs out and gradually drops below 30, is this normal? My last car had dummy gauges so I couldn't monitor it. Thanks

ps I did check the sellers work and it looked fine