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Discussion Starter · #1 ·
I recently found I had a misfire on cylinder 3, so I started by replacing all of the spark plugs and wires (the wires seemed to be OE). The 3rd cylinder spark plug looked in pretty bad shape but the misfire is still happening, when I start the truck sometimes it will start missing and the check engine light will flash, as soon as I start driving it stops flashing and seems to go away.
I haven't had to dig deeper than plugs for a misfire before, looking for suggestions on where to look next.
 

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Dirty injector or bad injector could be the cause. You can try running a high quality injector cleaner in it, the good ones contain PEA. Unfortunately the early spider injector setups like you have are known to be problematic as they age.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Also check your fuel pressure to ensure your fuel system is a) getting the proper pressure and b) not leaking. A leaky injector will show as a rapidly declining fuel pressure after priming the pump.
 

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just how old is the distributor cap and rotor?
 

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Since it's a specific cylinder (#3) and not a random misfire, it shd be easy.
Do the easy checks first.
  • get one of the old spark plugs and put it on the #3 wire and ground it. Start engine and see if you have spark.
  • if you have spark, then it's a fuel issue.
 
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