LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums - View Single Post - #3 cylinder mis-fire
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post #1 of (permalink) Old 05-25-2019, 08:03 PM Thread Starter
rmestate
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Join Date: May 2019
Posts: 4
 
#3 cylinder mis-fire

engine was missing at 180,000, so a cap & rotor seemed in order. water pump was also bad and a new one was installed along with a complete optispark from a well known vendor. the engine ran rough and inspection with a timing light showed #3 firing erratically; changed plug wire & plug and checked compression (which is 150psi) but erratic firing still present. removed distributor and checked cap which had zero resistance for #3. with further inspection, a scorch mark was seen on the plastic insulator plate. the mark went through and the metal plate was scorched on one side. it seemed that the plastic plate may have had a crack in the area where the plate drops. I installed a new plastic plate and new cap & rotor and the engine was still rough. Then i took one of my old optisparks and installed the new cap & rotor while keeping the OEM insulator plates. The car then ran great for about a mile. inspection revealed that, once again, only #3 was firing erratically. have not opened up the dizzy but i am expecting to see burn marks in the vicinity of #3 electrode....again
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