Five Needle Sweeps

1. With the engine off, disconnect the vacuum line to the EGR valve and connect a vacuum pump to the connection on the EGR valve.
2. Apply approximately 300 mbar of vacuum to the EGR valve and disconnect the vacuum source. The EGR valve should close with an audible sound. If the valve can be heard closing, then the valve is ok, proceed to step 4. If the valve cannot be heard closing, proceed to step 3.
3. Remove the EGR valve from the vehicle and apply approximately 520 mbar of vacuum to the valve. The valve should open fully. Disconnect the vacuum source, the valve should close with an audible sound. If the EGR fails any of the checks in this step, replace the EGR valve and proceed to step 4.
4. Tee into the vacuum line leading to the EGR valve. Connect a multimeter with the special test cable between the vacuum transducer and wiring harness. Start the engine and run it until a vacuum reading of approximately 250 mbar is reached. A voltage reading of 400 to 500 mA should be read at 250 mbar. If the reading is too low, check that the vent line to the passenger compartment and its filter is clear, cleaning or replacing as required, then proceed to step 8. If the reading is too high, proceed to step 5. If the reading is 0 mA, proceed to step 6.
5. Check vacuum supply line for blockage. Check the white/purple/brown vacuum line between the vacuum transducer and EGR valve for interruption. Check vacuum pump. If vacuum lines and vacuum pump are OK, replace EGR valve vacuum transducer and proceed to step 8.
6. With the engine off, ignition on, and the 2 pin plug on vacuum transducer disconnected, check the voltage to the vacuum transducer. If 12 volts is measured, proceed to step 7. If 12 volts is not measured, check and repair any open circuits. If no open circuits are present, replace the EDS control unit and proceed to step 8.
7. Tee into the EGR vacuum supply line with a vacuum gauge, run engine at 850 RPM and note the vacuum reading. Snap the throttle. Vacuum reading should drop when throttle is opened. If it does, proceed to step 8. If it does not, replace the EGR vacuum transducer and proceed to step 8.
8. Check the air flow sensor for binding. If binding is present, replace the air flow sensor.