Question about 1997 Pontiac Sunfire

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Missing, stalling Pontiac Sunfire

1997 Pontiac Sunfire is missing badly. Stalls and has no power. Also has gas smell. The OBDII codes are Throttle Position Sensor (P0121), Engine Misfire (P0141) and O2 Sensor (P0400).
I have replaced the Throttle position sensor and confirmed the voltages to the sensor; both are good, but this didn't fix the problem.
What else could cause this problem and these codes? Any help is appreciated.

Posted by John Jimison on

  • 4 more comments 
  • John Jimison May 31, 2009

    Replaced fuel pressure regulator and now the only error codes are misfires (P0400). The car is still missing, still need some suggestions.

  • John Jimison Jun 04, 2009

    Right, the only code left is random cylinder misfire (P0300). I think the problem is in the ignition and need to know how to isolate the problem to the coil packs, ignition control module or PCM without replacing them all.

  • John Jimison Jun 05, 2009

    If the air flow meter is a sensor then this car doesn't seem to have one. It doesn't show an air flow meter in the repair manual either. The only sensor to measure air flow that I'm aware of is the MAP sensor which has already been checked and replaced. If air flow meter means some kind of measurement you'll have to explain how to take the measurement.

  • John Jimison Jun 07, 2009

    Checked EGr and it isn't the problem. I did find a loose vacuum hose going to a gadget bolted to the side of the alternator. The gadget has an electronic connection and a vacuum hose that goes to the PCM. It doesn't show in my service manual so I don't know what it is, but even with the hose secure it still didn't fix the problem.

  • John Jimison Jun 10, 2009

    I found my problem with this car. There's no need to pursue this any further.

  • John Jimison Aug 17, 2009

    The problem was the coil pack housing. In this case the code for random cylinder misfires meant that two of the cylinders weren't firing. It was likely the coil pack or the housing.
    If you have an ohmmeter with a 20k (20,000) ohm or higher range you can check the resistance between the terminals on on the bottom of the housing. There should be resistance of around 5000 and 6000 ohms between the two outside pins (cylinders 1 and 4). There should be resistance of around 5000 to 6000 ohms between the two inside pins (cylinders 2 and 3). There shouldn't be a resistive path from the outside pine to the inside pins. If there are any resistive paths with the coil packs removed then the housing is bad.
    If any these measurements aren't right then you likely have a problem with a coil pack or the housing.



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Well tell everyone what the hell it was ,thats what this is for ********!!!

Posted on Aug 16, 2009



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The OBD II code for P0400 is Exhaust Gas Recirculation Flow Malfunction.
I'm sure the only thing you have left is you may have to replace the EGR valve or check for any leak from the vaccum lines going to to EGR valve.

Posted on Jun 01, 2009

  • Anonymous Jun 04, 2009

    The only thing is it's giving you a code P0300. If it was a code P0301, that would mean that cylinder 1 is misfiring. if it was P0302, that would mean that cylinder 2 was misfiring. You get the idea after that. The reason that is give a P0300 is because we have either multiple cylinders misfiring, or the computer simply can't determine the specific cylinder. So all the coils can't all go bad at the same time. I would look at the air flow meter and see what is going on there. Most likely the fuel mixture is way off causing the misfires. If the air meter is give the computer there is high volume of air, then the computer with put more gas in the cylinder. Therefore, with this problem at idle, the gas ratio would way up and not enough air the combustion chamber to fire properly. That way I think you smell unburnt gas. Check out the air flow meter first before the coil packs and ignition module.

  • Anonymous Jun 06, 2009

    Yep, that is the one. The MAP sensor does basically the same thing as a air flow sensor. If you checked the MAP sensor already and it's working ok, then the only thing I can think of that would cause the rich fuel smell would be the EGR ( Exhaust Gas Recirculation ) system. Too much Exhaust Gas is getting into the intake lowering the amount of fresh air going into the engine, causing misfire.

    The EGR system may not bad enough to throw a trouble code to itself, but bad enough to cause problems. Look for any vacuum leaks in the EGR system and check the EGR valve.

    That would be the next thing I would check.



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