Misfire round 5 - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-30-2012, 01:07 PM   #11
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fuel pressure problems will cause the injector problems and o2 codes. fuel pressure test would be next, though its more than likely your filter since its original. but could be pump, or fpr. whats the exact code number?
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Old 05-02-2012, 04:01 PM   #12
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I'm not sure anymore...UPDATE: I replaced the fuel filter and it didn't fix the problem completely. At certain times it is fine through all RPM ranges, but then you get on it again and it sputters, like it'* not getting enough fuel again until you get to 4500+rpm. I am not lacking power, just when it sputters. What gives? Next plan of attack is probably plug wires again, but I still think that it'* in the fuel system.(also,we did unplug the MAF Sensor, and it didn't help, just made it not want to run at all).
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Old 05-02-2012, 04:21 PM   #13
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sniff your vacuum line for your FPR, if gas vapors are present your FPR is bad. after that i would put a pressure gauge on it make sure your pump is putting out the right pressure.
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Old 05-08-2012, 09:46 AM   #14
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Well, the new fuel filter and new fuel pump didn't fix it(even though the computer said it was bad).....could a sensor or regulator that deals with the supercharger be the problem? I only starve when crossing the 0 mark on up on the boost gauge.
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Old 05-08-2012, 10:49 AM   #15
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Ignition misfires:
  • spark plugs
  • wires
Fuel misfires (lean due to too much air, or not enough fuel):
  • fuel pump
  • fuel filter
  • faulty injector(*) or the electronics that control them
  • EGR valve stuck open
  • leaking intake manifold gasket
  • defective MAF sensor
Mechanical misfires:
  • worn piston rings, valves, cylinder walls, or lobes on a camshaft
  • leaking head gasket or intake manifold gasket
  • damaged or broken rocker arms
  • slipped or incorrectly-installed timing belt or timing chain
Without a code to help narrow it down, based on your having replaced the fuel filter and pump, I would approach it in the following order:
  1. spark plugs
  2. wires
  3. Seafoam in the gas tank to clean the injectors
  4. listen to each injector for a mechanical clicking to indicate they are actuating (use a mechanic'* stethoscope)
  5. use a noid light (you can make one with a 12V bulb) to make sure each injector is getting a firing signal
  6. check the EGR valve to make sure it is not stuck open
  7. pull the rocker covers and inspect for damage to springs, rockers, etc.
  8. compression test each cylinder
My guess is you won't get past plugs and wires before you find the problem, but I obviously could be wrong.
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Old 05-08-2012, 11:17 AM   #16
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2kg4u forgot to mention that a clogged up catalytic converter can cause a misfire as well, usually a random one that will hop from cylinder to cylinder.
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Old 05-08-2012, 11:33 AM   #17
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Any restriction in the exahaust (clogged cat, pinched pipe) can cause a misfire. There are also several more possible causes. I was trying to hit the most likely ones.
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Old 05-08-2012, 11:41 AM   #18
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Gotcha. I'm just a big advocate for that because I've had a few cat'* get clogged and cause this. All fairly "soon" in their life too, all before 100k.
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Old 05-08-2012, 01:02 PM   #19
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I think if he had a plugged cat he would experience a loss of power above a certain RPM every time he drove, rather than a misfire that occurs at random times. You are right though in that nothing can be completely ruled out just yet.
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Old 05-08-2012, 05:11 PM   #20
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He says it does it once it gets into boost, so that'* above a certain power range?
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