Question about 2004 Pontiac Grand Prix

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2004 Grand Pix starting running rough all of the sudden. I tuned it up and replaced the engnition module and it still running rough any suggestions?

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  • Randy Ault Nov 08, 2010

    I do not have awesome power. No injector problems. It runs like it out of time

  • Randy Ault Nov 08, 2010

    no other codes. It runs like it is out of time

  • Randy Ault Nov 14, 2010

    Ok I had a exhaust valve spring that was broke I have replaced it. It is running better but still rough and showing multiple cylinder misfire. Any idea what is still wrong?


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  • Pontiac Master
  • 6,826 Answers

Electronic Engine Controls WARNING
To avoid personal injury and/or vehicle damage, refer to the service precautions at the beginning of this section.
General Information The Engine Management System (EMS) uses several different sensors and actuators to gather and control various emissions and driveability aspects of the vehicle. These may include but are not limited to:

  • MAP - Manifold Absolute Pressure Sensor
  • BARO - Barometric Pressure Sensor
  • FTP - Fuel Tank Pressure Sensor
  • ECT - Engine Coolant Temperature Sensor
  • A/F - Air Fuel Ratio Sensor
  • APP - Accelerator Pedal Position Sensor
  • CKP - Crankshaft Position Sensor
  • CMP - Camshaft Position Sensor
  • EGR Valve Position - Exhaust Gas Recirculation Valve Position Sensor
  • HO 2S - Heated Oxygen Sensor
  • IAC - Idle Air Control Valve
  • IAT - Intake Air Temperature Sensor
  • KS - Knock Sensor
  • MAF - Mass Air Flow Sensor
  • TP - Throttle Position Sensor
Are there any codes that point to a problem with any of the above sensors?

Posted on Nov 08, 2010

  • 5 more comments 
  • Randy Ault Nov 08, 2010

    Code PO300 multiple cylinder misfire

  • Duane Wong
    Duane Wong Nov 08, 2010

    OK, if you have a multiple cylinder misfire, there could be an HO 2S heated oxygen sensor problem.

    Any other codes?

  • Duane Wong
    Duane Wong Nov 08, 2010

    What gets me is .. how can it have a multiple cylinder misfire and still have awesome power.

  • Duane Wong
    Duane Wong Nov 08, 2010

    Could the fuel injectors be clogged up?

  • Duane Wong
    Duane Wong Nov 08, 2010

    Timing Chain & Gears

    Removal & Installation

    3.8L Engine

    To Remove:

    1. Remove the engine front cover.
    2. Align the timing marks on the sprockets.
    3. Remove the timing chain dampener bolt and remove the damper.
    4. Remove the camshaft sprocket mounting bolt.

      Timing chain & sprockets 3.8L

    5. Remove the camshaft sprocket and timing chain.
    6. Remove the balance shaft drive gear if removing the camshaft thrust plate bolts.

      Balance shaft gears 3.8L

    7. Remove the balance shaft driven gear mounting bolt and driven gear if removing the balance shaft.
    8. Clean and check all components for wear and damage.
    9. If the pistons moved in the engine, use the following procedure:

      1. Rotate the crankshaft until number one piston is at top dead center.
      2. Rotate the camshaft with the sprocket temporarily installed until the timing mark is straight down.

    To Install:

    Balance shaft gears 3.8L

    1. If removed install the balance shaft driven gear with the mounting bolt. Tighten 16 ft-lb (22 Nm). Tighten an additional 70 degrees.
      NOTE: Prevent the balance shaft from rotating and install the balance shaft driven gear bolt, if required.

    2. Align the timing marks on the balance shaft drive gear and balance shaft driven gear.
    3. Install the crankshaft sprocket.

      Timing chain & sprockets 3.8L

    4. Place the timing chain around the camshaft sprocket and on the crankshaft sprocket with the timing marks in alignment.
    5. Install the camshaft sprocket on the camshaft with the mounting bolt. Tighten 74 ft-lb (100 Nm). Tighten an additional 90 degrees.
    6. Install the timing chain dampener with the mounting bolt. Tighten 16 ft-lb (22 Nm).
      Rotate the engine two revolutions and ensure that the timing marks are in alignment.

    7. Install the engine front cover.

    5.3L Engine

    To Remove:

    1. Remove the oil pump from the engine.

      Timing marks

    2. Turn the crankshaft until the crankshaft and camshaft sprockets are aligned.

      Crankshaft sprocket removal and installation

    3. Remove and discard the camshaft sprocket bolt.
    4. Remove the camshaft sprocket with the timing chain from the camshaft.

      Timing chain tensioner removal and installation

    5. Remove the mounting bolts and remove the timing chain tensioner from the engine.

      Crankshaft sprocket removal

    6. Using special tools J 41816-2 crankshaft end protector, J 41558 crankshaft sprocket remover, bolts, and J 8433 puller bar or equivalent tools, remove the crankshaft sprocket from the camshaft.
    7. Remove the crankshaft sprocket key from the crankshaft.

    To Install:

    1. Install the crankshaft sprocket key into the crankshaft.
    2. Align the crankshaft sprocket with the crankshaft sprocket key.
    3. Using special tools J 41478 crankshaft front oil seal installer, J 41665 crankshaft balancer and sprocket installer or equivalent, install the crankshaft sprocket onto the crankshaft.
    4. Turn the crankshaft until the alignment mark is in the 12 o'clock position.
    5. Compress the timing chain tensioner guide and install special tool EN 46330 into the timing chain tensioner guide to lock it.
    6. Install the timing chain tensioner on the engine with the mounting bolts. Tighten 18 ft-lb (25 Nm).
    7. Install the camshaft sprocket with the timing chain onto the camshaft.

      Timing marks

    8. Ensure the camshaft sprocket alignment mark is in the 6 o'clock position.
    9. Remove the special tool EN 46330 from the timing chain tensioner.
    10. Install the flywheel onto the crankshaft.
    11. Install special tool J 42386-A flywheel holding tool on the flywheel. Tighten the bolt 37 ft-lb (50 Nm).
    12. Tighten the camshaft sprocket bolt 55 ft-lb (75 Nm) plus an additional 50 degrees.
    13. Remove the holding tool and flywheel.
    14. Install the oil pump.

    Previous Next

  • honeymokey
    honeymokey Nov 09, 2010

    I doubt is has bad timing gears,chain. They do not go bad on a 3800 engine. Mine has over 300k on it. You most likely have a bad coil or coils. Check for vacuum leak also.

  • Randy Ault Nov 14, 2010

    I had broken exhaust valve spring. I have replaced it but it is still roughing rough and showing multiple cylinder misfire. Any idea what still might be wrong


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