97 chevy vortec 4.3 multiple misfires

[jcoffer]

I have a 97 chevy that runs very rough. I have done multiple tuneups, used professional injector cleaner, replaced coil, fuel pump, and pickup module. Using OBDII reader I get multiple misfires and sometimes specifically cylinder 2 misfire. vehicle has only 61K miles and was parked at airport for weeks frequently. Running problem has gotten so bad that truck has left me on side of road twice where replacing the cap and rotor got it running again, but still running rough. Need idea if MAP or other sensor could be problem. Can not afford dealership hit or miss part swapping solution. Any Ideas?

[jimss454]

Remove cap & rotor. Try blasting air with blowgun in & around distributor, especially around edges of the "breaker plate". Tiny balls of conductive white material form inside cap, and if they get down under plate where the magnetic pickup/rotor wheel are, they can cause intermittent shorting, and drive you nuts. Sometimes the rascals cannot be dislodged. If possible, try substituting a known-good distributor to confirm. Worked for me, after changing numerous other parts. (Thought it was in-tank fuel pump, because everytime the ignition would cut-out, the ECM woud temporarily halt the injectors from spraying fuel. I thought this was the cause of the misfire, but it was a symptom).
Let us know if this helps, or what you find out! Good luck, -Dan.

[jcoffer]

Originally Posted by jimss454

Remove cap & rotor. Try blasting air with blowgun in & around distributor, especially around edges of the "breaker plate". Tiny balls of conductive white material form inside cap, and if they get down under plate where the magnetic pickup/rotor wheel are, they can cause intermittent shorting, and drive you nuts. Sometimes the rascals cannot be dislodged. If possible, try substituting a known-good distributor to confirm. Worked for me, after changing numerous other parts. (Thought it was in-tank fuel pump, because everytime the ignition would cut-out, the ECM woud temporarily halt the injectors from spraying fuel. I thought this was the cause of the misfire, but it was a symptom).
Let us know if this helps, or what you find out! Good luck, -Dan.

Removed cap and blew out distributor with canned air. Truck is running better but I am still getting "Multiple Random Misfires". I am going to run it for a few more days, currently, the last 2 days have returned no new codes after resetting them from the multiple misfire. I also have replaced the MAP sensor during the distributor cleaning. It helped slow down the idle. I also noticed the 2 hold down screws on the rotor were discolored on the spark side. Just to help cut down contributors, I covered them with RTV. If I get no new codes within the next 5 days, I will consider the problem solved by your suggestion.
Thanks.