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Hi every one my name is Gary. little background I'm a foreman for a heavy highway construction company and have a passion for working on cars. i would consider myself a highly advanced diy guy. that said said I currently have a 98 Chevy K1500 with 5.7 and a fairly frequent number 4 misfire and a much more random number 6 misfire. When taking out the plugs for visual inspection number 4 was almost completly carboned shut and number 6 was not far behind. 2 and 8 looked perfect. test i have done include the following:
Fuel pressure steady around 60 while running.
injector balance test with all cylinders with near same results, pump on 60psi, pump off 55psi , after injector pulse 47psi
I put an inline spark tester on 4 and 6 with strong and steady spark.
Compression test of all bank two cylinders all 150 - 155
I don't have a leak down tester but put 100 psi in cylinder at TDC and had what i believe to be reasonable leakage into crank case and a little out of the exhaust pipe.
fuel trim while the misfire was occurring were both close to zero.
I feel as if Im forgetting something simple all comments on possible direction would be appreciated.
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