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Random cylinder Misfire

9K views 9 replies 6 participants last post by  Timmyblazer33 
#1 ·
On my 2002 GMC Envoy I got a random cylinder misfire reading. I changed all six spark plugs and the crankshaft position sensor. Still runs rough though. SES light is blinking. Any ideas of what to fix next?
 
#3 · (Edited)
Ooohhhhh,just had same the same problem 6 mos ago. Multi misfire. Purchased 2 new coils,swapped one out then tested with OBDII. Kept testing until the meter told witch cylinder was misfiring. Repaired 1st and 3rd coil pack from front of truck. 1mos ago happened AGAIN! Had to change remaining 4! I bought them at several auto zone locations,cause they only stock one or two. They go for about 65-70,a piece. :suicide:Truck runs awesome! Did these,new plugs,and throttle body cleaning. Truck is BEAutiful. Good luck trouble shooting, definately need a meter to isolate multi misfire code. Once ya know which cylinders are defective it is an easy fix. 10mm socket for the coilpacks and breather cover,and throttlebody.:woot:http://forums.trailvoy.com/showthread.php?t=48277&page=2. This thread may help.
 
#4 · (Edited)
Most likely bad coil pack(s). Since it's a 10 yr old vehicle, I'd recommend changing all six coils......should take care of the problem. I had same issue w/ blinking SES light.....replaced all coils, problem disappeared.

BTW, what plugs did you put in it?

Oh, and double check to make sure you seated the tip of the coil pack straight down and onto the spark plug.....the coil CAN be inserted slightly crooked and not touch the plug.
 
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