my 96 blazer keeps getting the above codes at least once or twice a week.
engline light pops on after driving a few miles. usually happens on the same stretch of road in the am while driving to work. engine will miss,stumble and run badly for about 10 seconds setting the engine light on and 30 seconds later all is well. complete tuneup done(plugs,cap,rotor,etc) 3 weeks ago.also might add that i was getting about 200-240 miles per tank of gas.now i'm lucky to make 160-180 miles per tank.other than the issues as explained the truck runs fine and has good power.i realize there are some consessions to be made for the truck being 180,000 miles old,but what could be causing the random miss fires. besides the tuneup i have replaced in the last 6-8 months
fuel pump,egr,mass air flow,spider injection system,ckp sensor and map sensor.

 

try checking the distributor gear for wear. my truck had the same codes and that took care of it

 

if it is the the gear i'll assume to replace the entire dist.can you recommend a distributor brand and should it be purchase with or without the module. what about the ignition coil,should this be a consideration.all parts except for the above mentioned in original question are original.need to get it right the 1st time. gas is getting quite expensive. i might add that at times when this mis fires happens it feels like i'm towing something.

 

if you get a distributor, i would get a cardone rebuilt from advance auto. it should be part# 30-1639 ....its basically a GM original thats rebuilt and fits well... but if you insist on new aftermarket, you should get a summit dist. part# sum-850097 and costs $150 which is double the price of the rebuilt cardone unit from advance..... the other thing i want to mention is that when you take the original dist. out, it is possible that the gear may look fine. but the dist. still may be your problem because sometimes the center distributor shaft slips inside the rotor base now throwing the timing off...and thats what happened to mine....

 

WARNING!!! be extremely careful when tightening the screws mounting the cap to the distributor if that cap is plastic like on my 97. I had an occasional miss, and the guy I paid to dig into my fuel system and engine trying to find it overtightened and cracked the housing. I wasn't aware of this until 4 months later when I took it to another better known mechanic for a follow up and he found the mess.