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got a miss all of the sudden,and went away.untill three weeks later ( 3 days ago) went to the shop and the code said #4 misfire....120,000 miles on car just bought 4 months ago we replaced the plugs and #6 fuel enjector....still missing.... checked fuel pump and with key on and with truck running pressure is at 60lbs. got any ideas?


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Location: Oregon
I don't understand... you have a misfire on #4 and you do plugs and #6 injector???

so, was the code a p0304? did you graph the misfire counter? What cylinder does the scanner show when the engine is actually missing? What made you decide to change #6 injector?

I know I am not giving you anything that is helpful right now but I am trying to find out what is going on with your vehicle and why you have done the things you have done.

If I had a vehicle with misfire, a scanner that showed a misfire code, I would look to verify the cylinder that is misfiring is the same as the one the scanner says. If the actual and the scanner match concentrate on that one. Spark, compression and fuel. Look at the fuel trim for the bank with the miss. I might even check with the 4 or 5 gas analyzer. If you have high hydrocarbons out the tailpipe in pull the injector connector and see if the HC'c drop. If the HC's drop then you have a spark problem. If you have higher O2 but HC's are reasonable look at the injector. A simple switch of two close injectors and watch the misfire counter to see if the miss follows the injector or not. possible Coil, wire and plug too. (5.3L) Coil, boot and plug (4.2)


   
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was planning a tune up anyway before the miss started.replaced #6 injector because it was wet around it and we ohm'd it out and it read 14.9 ohms the other 7 read 13.3 so i had them replace it..it is a 5.3 with p0304 code the only thin not new is coil pack.has all new plugs and wires.


   
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try switching the coil between #4 and #2 and see if the code changes to a p0302


   
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Is it comman for it to smoke after idling for a few minutes with a misfire?


   
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no, not usually. It is normal to have water vapor until the exhaust pipe vaporizes the condensation in the exhaust pipes. Is the smoke white? Blue? Black?


   
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My 2004 gmc envoy vibrates when idling at lights ect... I was told it may be the coil pac.. Wat is the coil pac and can it be that... Thanks


   
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