Exhaust Gas Recirculation (EGR) Systems 10A13 EGR System Functional Diagnosis TEST STEP RESULT P ACTION TO TAKE EGRl CHECK SYSTEM INTEGRITY 0 Check vacuum hoses and connections for Yes F 60 to -. looseness, pinching. leakage, splitting, No } SERVICE EGR system blockage and proper routing. as required. I Inspect EGR valve for loose attaching bolts or RE-EVALUATE damaged flange gasket. symptom 0 Does system appear to be in good ' condition and vacuum hoses properly routed? E682 CHECK EGR VACUUM AT IDLE 0 Run engine until normal operating temperature Yes D GO to -. is reached. N P RECONNECT EGR 0 With engine running at idle, disconnect EGR o vacuum hose. vacuum supply at the EGR valve and check for INSPECT EVR solenoid avacuum Slgnal. forleakage. RUN NOTE: The EVR solenoid has a constant QUICK Te- internal leak. You may notice a small vacuum signal. This signal should be less than 3.4 kPa (1.0 in-Hg) at idle. o Is EGR vacuum signal less than 3.4 kPa (1.0 in-Hg) at idle? EGR3 [ CHECK EGR VALVE FUNCTION 0 install a tachometer, Rotunda 059-00010 or Yes > The EGR valve is OK. equivalent. UNPLUG and 0 Disconnect the Idle Air Control (IAC) solenoid RECONNECT the EGR (9F715) electrical connector. valve vacuum supply 0 Remove and plug the vacuum supply hose hose. RECONNECT from the EGR valve nipple. the lACsolenoid 0 Start engine, idle with transmission in connector. REFER to NEUTRAL, and observe idle speed. It Diagnostic Routines, necessary. adjust idle speed according to Section 2A. 390 9A- No > INSPECT the EGR NOTE: If the engine will not idle with IAC solenoid disconnected, provide an air bypass to the engine by slightly opening the throttle plate or by creating an intake vacuum leak. Do not exceed a typical idle rpm. Slowly apply 5-10 inches of vacuum to the EGR valve nipple using a hand vacuum pump, Rotunda 021-00014 or equivalent. Does idle speed drop more than 100 rpm with vacuum applied and return to normal (i 25 rpm) after the vacuum is removed? valve for blockage or contamination. CLEAN the valve using Rotunda 021-80056 EGR valve cleaner. INSPECT valve for vacuum leakage. REPLACE if necessary. 1994 Powertrain Control/ Emissions Diagnosis July, 1993