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When I start my 1999 chevy pickup with the 325 engine, I ...

Sent to Chevy Experts August 8 2008 at 8:51 AM
   

When I start my 1999 chevy pickup with the 325 engine, I can go down the road to a store, I can come back out and go to start my truck and she won''t start until I put my foot on the accelerator. Now keep in mind she turns over fine, it just won''t start until I put my foot on the gas. What would cause this problem?

 

Optional Information:
1999 Chevrolet z71 4x4 325

Already Tried:
change gas filter

Customer (name blocked for privacy)
Answer
August 8 2008 at 9:10 AM (19 minutes and 42 seconds later)
         
ACCEPTEDCheck Mark

replace the idle air control valve. good luck. i hope i helped and please accept my answer. thanks T-MAN

Idle Air Control Valve Replacement

Removal Procedure



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  1. Disconnect the IAC valve electrical connector.

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  2. Remove the IAC valve attaching screws (4).
  3. Remove the IAC valve (3).
  4. Remove the IAC valve O-ring seal (2).

    Notice:

    Do Not push or pull on the IAC valve pintle on IAC valves that have been in service. The force required to move the pintle may damage the threads on the worm drive.
    Do Not soak the IAC valve in any liquid cleaner or solvent, as damage may result.

     

  5. Clean the IAC valve O-ring sealing surface, the pintle valve seat, and the air passage.
    Clean the IAC valve using GM cleaner XXXXXXX or GM X-66A. Use a shop towel or parts brush to remove heavy deposits.
    If the air passage has heavy deposits, remove the throttle body for complete cleaning.
    Shiny spots on the pintle or seat are normal, and do not indicate misalignment or a bent pintle shaft.
  6. Inspect the IAC valve O-ring for cuts, cracks, or distortion. Replace the O-ring if it is damaged.

Installation Procedure



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    Important: If installing a new IAC valve, be sure to replace it with an identical part. The pintle shape of the IAC valve and the diameter of the IAC valve are designed for the specific application.

  1. Measure the distance between the tip of the IAC valve pintle and the mounting surface (1). If the distance is greater than 28 mm (1.1 in), use finger pressure to slowly retract the pintle. The force required to retract the pintle of a new valve will not cause damage to the valve.

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  2. Lubricate the IAC valve O-ring (2) with clean engine oil.
  3. Install the IAC valve O-ring (2) on the IAC valve (3).
  4. Install the IAC valve (3).
  5. Apply Loctite 262 to the IAC valve attaching screw threads if necessary.

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  6. Install the IAC valve attaching screws (4).

    Tighten
    Tighten the IAC valve attaching screws to 3 N·m (27 lb in).



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  7. Connect the IAC valve electrical connector.
  8. Perform the Idle Learn Procedure. Refer to PCM Idle Learn Procedure .

Idle Learn

Idle Learn Procedure

Anytime the powertrain control module (PCM) or the battery is disconnected, the PCM loses power, or the PCM is reprogrammed, the PCMs learned idle position is lost. The engine idle is unstable when the learned idle position is lost.

Perform the following procedure in order to return the learned idle to the correct position:

Automatic Transmission

  1. Turn OFF the ignition.
  2. Restore the PCM battery feed.
  3. Turn OFF the A/C controls.
  4. Set the parking brake and block the drive wheels.
  5. Start the engine.
  6. Ensure that the engine coolant temperature is more than 80°C (176°F).
  7. Shift the transmission into Drive.
  8. Allow the engine to idle for 5 minutes.
  9. Shift the transmission into Park.
  10. Allow the engine to idle for 5 minutes.
  11. Turn OFF the engine for 30 seconds.

Manual Transmission

  1. Turn OFF the ignition.
  2. Restore the PCM battery feed.
  3. Turn OFF the A/C controls.
  4. Set the parking brake and block the drive wheels.
  5. Place the transmission in Neutral.
  6. Start the engine.
  7. Ensure that the engine coolant temperature is more than 80°C (176°F).
  8. Allow the engine to idle for 5 minutes.
  9. Turn OFF the engine for 30 seconds.
Answer
August 8 2008 at 9:57 AM (46 minutes and 40 seconds later)
         
You need to clean the throttle body and throttle blade. Remove the air intake duct and clean the throttle body and throttle blade with some carburetor cleaner spray. Do this with the engine running so the Idle Air Control valve gets cleaned as well.


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