code 12

ok i did the diagnostic thing with the paper clip, all i got out of it was flash , pause flash,flash. helg the clips on for about 2 min and kept getting same sequence. 91 lumina , 3.1 . replaced timing chain cause old 1 broke, put in new plugs, cleaned idle air valve and the dmn thing still aint right. it starts and idles but acts like it has a miss in it when you drive it, what else should i do.

Recheck the timing belt alignment

code 12 represents the system is in diagonstic mode basiclly. Its not really a problem code. If its missing, and a timing chain went, its a good idea to get a compression test done on it and make sure all cylinders are holding compression and there is not something bent or broken internally.

Lumin maddness, the 3.1 doesn't have a timing belt.

As blazes9395 stated, you need to do a compression test to see if you have any bent valves. Even though the book doesn't show the 3.1 as an interference engine (meaning that if the timing chain goes, the valves will get hit by the piston), they are known for this type of damage. The 3.1 has a known issue with piston slap due to the high mounted rings allowing the piston to rock back and forth in it's bore. As this gets worse, the piston gets closer to the valves at the top of the stroke. If the chain breaks, the valves stay open, and the piston hits them.