I have a 89 5.0 supercharged. The car was tuned then blew a head gasket. After the head gasket was changed i didnt think that i had my timing right so i took the car back to the tuner because i thought the timing had to be set with the computer(i didnt know). So the tuner was trying to time it and said it wouldnt hold time. He thought it could be the ignition module, so i changed that and was trying to set the timing myself and when i go to 10 degrees the car runs like ****. Is the stock timing 10 atdc or btdc? I think the tuner marked the 10 to the right of the 0. If i go to that the car runs bad. When i go the other way it runs alot better but i know thats not right.

Please help

 

Are you checking timeing with the spout connector out??? Run codes to see what's going on

 

Yes the spout connector is out. Its on 10 now but when you bring up the rpms to about 4000 and let it back off it has a very slight rumble / backfire. What could that mean?

 

taking a shot in the dark here but, i would look at the timing chain or distributor.