Ok where do I start? I recently bought this 1991 ford bronco with a 302 and a rebuilt transmission in it. It has a 6 inch lift and 35 inch tires. Some days it runs perfect but most days it gives me problems. For starters it will just randomly rev itself up when it is idling. Then it will load up and start blowing out black smoke which tells me it is running real rich. And sometimes when i'm driving it will just randomly die and not start back up for about 30 seconds. And finely when i'm driving down the road the check engine light will randomly come on and the transmission will slip real bad. It has plenty of fluid and it was recently rebuilt, I have receipts, after a little bit the check engine light will go out and it will shift normally. It doesn't do this every time but I know it's not good for it. Sorry for the long post but i'm just real frustrated and I have no clue where to start. Any help will be appreciated.

 

Since it is a 91 it has to have some rust and corrosion and that could include the electrical connections. For starters I would make sure every ground connection I could find was clean and in good shape. There are many of them and it will take some time , but it will do no harm and might help solve the problem.

 

Ok the bronco is fixed. I plugged up every single vacume line that wasn't necessary for the motor to run. Then I cleaned every electrical connection that I could find and then put a new fuel filter on. I drove it 60 miles with absolutely no problems what so ever and I can tell that my fuel mileage even went up. I really love this bronco now.