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EGR Function Testing - General Motors - Imports Geo Storm I

Emission Applications 3 illustrations ~740 words

All Models Except 1988-93 LeMans (Ported EGR Valve)

  1. Ensure engine is at normal operating temperature. Disconnect vacuum hose at EGR valve. Connect a hand-held vacuum pump to EGR valve. Start engine.
  2. Apply vacuum to EGR valve. If engine runs rough or stalls, and gauge holds vacuum, EGR valve is functioning properly. Connect a vacuum gauge to EGR hose. Increase engine speed to about 3000 RPM. If vacuum is shown on gauge, system is functioning properly.

1988-93 LeMans (Positive Backpressure EGR Valve)

  1. Firmly grasp top of EGR valve and check for looseness by trying to rotate valve in both directions. If looseness is felt, EGR valve is defective. Ensure engine is at normal operating temperature.
  2. With engine idling, push up on underside of EGR diaphragm. If idle speed drops, EGR valve is functioning properly. Observe EGR valve diaphragm and increase engine speed to 2000 RPM. If EGR valve diaphragm moves, EGR system is functioning properly.

Metro

  1. With engine cool, ensure EGR valve is not loose or broken. Replace if necessary. Start engine and warm to normal operating temperature. WARNING: Wear gloves while testing EGR valve to prevent injury from burns.
  2. Place finger on bottom of EGR valve diaphragm. Increase engine speed. Note if EGR valve diaphragm moves. If diaphragm does not move, allow engine to idle. Disconnect vacuum hose from EGR valve. (Scheme 3) Apply 8 in. Hg of vacuum to EGR valve and place finger on diaphragm. Vacuum should hold, diaphragm should move and engine may stall. If EGR valve operation is as specified, go to next step. If EGR valve operation is not as specified, replace EGR valve.
  3. Check for carbon in valve which may cause a restriction. Restriction may be small enough so that engine may stall, but large enough to cause DTC P0400 to set. If EGR valve is okay, check EGR pressure transducer. If EGR valve is not okay, replace valve.

Scheme 3

Scheme 3
Scheme 3

Prizm

  1. With engine cool, remove EGR pressure transducer cap and filter. Check filter for contamination or damage. Use compressed air to clean filter, or replace filter if damaged. Install filter with coarser side facing outward and reinstall cap. (Scheme 4)
  2. Using a tee connector, connect a vacuum gauge between EGR valve and EGR pressure transducer. (Scheme 5) Start engine and check EGR valve seating by making sure that engine idles normally. If idle is okay, go to next step. If idle is rough and no other problems exist, replace EGR valve.
  3. Connect a jumper wire between duty check DLC terminals E1 and TE1 (located in engine compartment). With engine coolant temperature less than 117°F (47°C), accelerate engine to 2500 RPM and check vacuum gauge. If vacuum gauge indicates zero vacuum, go to next step. If vacuum is present, check EGR SOLENOID VACUUM VALVE (EGR-SVV).
  4. Run engine until engine coolant temperature is greater than 127°F (53°C). Accelerate engine to 2500 RPM and check vacuum gauge. If vacuum gauge indicates low vacuum, go to next step. If vacuum gauge indicates zero vacuum or high vacuum, check EGR SOLENOID VACUUM VALVE (EGR-SVV) and check EGR VACUUM PRESSURE TRANSDUCER.
  5. Remove vacuum gauge. Using a hand-held vacuum pump, apply vacuum to EGR valve. Engine should run rough or stall. If engine runs and idles okay with vacuum applied, replace EGR valve. Ensure vacuum hoses are correctly installed. Remove jumper wire from duty check DLC.

Scheme 4

Scheme 4
Scheme 4

Scheme 5

Scheme 5
Scheme 5

Tracker

  1. Raise and support vehicle. Place transmission in Neutral. Spin rear wheels while testing. EGR solenoid will not open without a vehicle speed input. Start engine. Increase engine RPM and ensure EGR valve does not operate with coolant temperature less than 131°F (55°C). Go to next step.
  2. Allow engine to reach normal operating temperature. Increase engine RPM and observe EGR diaphragm. If diaphragm moves, go to next step. If diaphragm does not move, check for misrouted, restricted, clogged or deteriorated vacuum hoses. If vacuum hoses are okay, check EGR valve. If EGR valve is okay, check EGR pressure transducer. If EGR pressure transducer is okay, go to step 4).
  3. Using a shop towel or glove, open EGR valve by hand with engine running. Engine should idle rough or stall. If idle does not change, remove EGR valve and clean EGR passage. Retest system. If engine runs rough or stalls, system is okay.
  4. Check EGR solenoid vacuum valve, EGR system check valve, related components and PCM. See DTC P0400 in TESTS W/CODES article.

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