ok i got an 89 s10 blazer4.3 4x4 auto that runs rough and sometimes backfires through the intake. replaced the plugs wires caps and rotor button. also has a shifting problem shifts hard and sometimes slips between gears. it throw a code for rich exhaust one time and hasnt given it again. and it will clear up a little and then get bad again. any ideas would be great.


thanks alot

 

timing chain

 

they

 

thanks ill check it

 

You may want to also check for a vacuum leak at the base of the throttle body.