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Old 03-12-2011, 07:09 PM
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Default Looking for input with 2002 silverado 1500 5.3L multiple cylinder misfire

Anyone have any input to what maybe my problem? I have a 2002 silverado 1500 5.3L (vortec) with multiple cylinder misfires. I changed the plugs & wires. but no change? Check engine light is on and got codes for multiple cylinder misfires and lean.
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Old 03-12-2011, 07:37 PM
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Lean code both banks? If so, there's too much unmetered air or not enough fuel. The usual suspects are air/vacuum leak, inaccurate MAF sensor, low fuel pressure, etc. Can you post the freeze frame data to go with whichever the trouble code may be?
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Old 03-12-2011, 08:16 PM
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Dont have the info infront of me. I had someone do the diagnostic on it and they told me multiple cylinder misfires and two lean codes. Someone also told me it may be the crank position sensor? what do you think?
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Old 03-13-2011, 10:23 AM
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The PCM detects misfires by minute changes in the crankshaft speed based on the CKP sensor. Your problem seems to be misfires from running lean, not isolated to a particular bank or cylinder.
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Old 03-13-2011, 12:22 PM
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Going to check for vacuum leaks today. How much fuel pressure should i have and do you think it maybe a bad MAF sensor? Any tests in mind i can try to single out the problem?
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Old 03-13-2011, 12:39 PM
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The MAF sensor is kind of hard to test. Try spraying it down with an appropriate cleaner. The KOEO fuel pressure 55-62 psi for 5.3L (2002-03). Vacuum leak? I don't know, inspect hoses/cracks and then spray TB cleaner into suspected spots with engine on?
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Old 03-16-2011, 07:24 PM
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Couldn't find any air/vacuum leaks. Moving on to fuel pressure. Think its possible the MAF sensor just went screwy and may need to be replaced?
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Old 03-17-2011, 11:17 AM
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It could be the MAF sensor if it's reporting too little air. It could also be an air leak past the sensor or an increase in the air duct diameter at the sensor (greater volume of air at given air speed).

It could be the O2 sensors if they are reporting too much oxygen in the exhaust. It could also be exhaust gas leak that flows past the outside of the sensors since they measure the difference in oxygen content inside vs. outside.

It could be the fuel supply side. The fuel metering is calibrated to the fuel pressure. There's a lot of could-be's that you'll have to work through.
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Old 03-21-2011, 10:43 PM
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my 04 had this same problem about a week after i bought it in 07 turns out the strainer had come off of my fuel pump and there was trash getting by the pump and stopping up my injectors. but in your case being you have and external fuel filter i doubt that could be it but its worth checking into
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Old 04-09-2011, 07:30 PM
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Question 1991 chevy 1500 skipping

I'm new..... but need help please! I put plugs, plug wires, rotor button, dis. cap, still skips. Did code reading, but only shows 12. when setting idling it skips but when you go up mountain its really bad. Any ideas? I'm ready to scream. It's a 1991 chevy 1500.
has 5.7 350, 4 wheel drive.
Thanks
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02, 2002, air, chevy, code, cyclinders, cylinder, engine, fuel, leak, low, misfire, multiple, pressure, silverado, trouble

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