Test 16: Metro
- With engine cool, ensure EGR valve is not loose or broken. Replace as necessary. Start engine and warm to normal operating temperature.
- Place finger on bottom of EGR valve diaphragm. Increase engine speed. EGR valve diaphragm should move. If diaphragm does not move, allow engine to idle. Disconnect vacuum hose from EGR valve. See Fig 1.
- Apply 8 in. Hg of vacuum to EGR valve and place finger on diaphragm. Vacuum should hold, diaphragm should move and engine should run rough and may stall. If EGR valve operation is as specified, go to next step. If EGR valve operation is not as specified, replace EGR valve.
- Check for carbon in valve which may cause a restriction. Restriction may be small enough so that engine may not stall, but large enough to cause DTC P0400 to set.
Courtesy of GENERAL MOTORS CORP.