How do I test if my EGR valve is working?

Per step EGR3: install a tachometer, disconnect the IAC solenoid (9F715) connector, remove and plug the vacuum supply hose from the EGR valve nipple, idle in NEUTRAL, then slowly apply 5-10 inches of vacuum to the EGR valve nipple with a hand vacuum pump. If idle speed drops more than 100 rpm with vacuum applied and returns to normal (±25 rpm) when removed, the EGR valve is OK.

How much vacuum should the EGR valve see at idle?

With the EGR vacuum supply disconnected at the valve, the vacuum signal should be less than 3.4 kPa (1.0 in-Hg) at idle. The EVR solenoid has a constant internal leak, so a small vacuum signal is normal.

What should I do if the EGR valve fails the vacuum function test?

Inspect the EGR valve for blockage or contamination, clean it using Rotunda 021-80056 EGR valve cleaner, inspect the valve for vacuum leakage, and replace it if necessary.

What if the engine won't idle with the 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.

What tools does the EGR functional test require?

A tachometer (Rotunda 059-00010 or equivalent) and a hand vacuum pump (Rotunda 021-00014 or equivalent); Rotunda 021-80056 EGR valve cleaner is used if the valve is contaminated.

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1994 Ford Bronco EGR System Functional Diagnosis - Test Steps EGR1-EGR3 (10A-13)

Ford EGR system functional diagnosis flow chart 10A-13 with vacuum and valve test steps

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Ford EGR system functional diagnosis chart (page 10A-13): step-by-step pinpoint tests for vacuum integrity, EGR vacuum at idle (<1.0 in-Hg) and EGR valve function using a tachometer.

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This page (10A-13) from the 1994 Ford Powertrain Control / Emissions Diagnosis manual (dated July 1993) presents the 'EGR System Functional Diagnosis' — a three-step pinpoint test chart for the Exhaust Gas Recirculation system. Step EGR1 checks system integrity: inspecting vacuum hoses for looseness, pinching, leakage, splitting, blockage, and routing, and checking the EGR valve for loose bolts or a damaged flange gasket. Step EGR2 checks EGR vacuum at idle: with the engine at operating temperature, the EGR vacuum supply is disconnected at the valve to verify the vacuum signal is less than 3.4 kPa (1.0 in-Hg); it notes the EVR solenoid has a constant internal leak. Step EGR3 tests EGR valve function: install a tachometer (Rotunda 059-00010), disconnect the IAC solenoid (9F715) connector, plug the vacuum supply hose, and apply 5-10 inches of vacuum to the EGR valve nipple with a hand pump (Rotunda 021-00014); idle speed should drop more than 100 rpm and return to normal (±25 rpm) when vacuum is removed. Each step gives Yes/No results with actions such as servicing the system, inspecting the EVR solenoid, running the Quick Test, or cleaning the EGR valve with Rotunda 021-80056 cleaner.

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Frequently asked questions

How do I test if my EGR valve is working?: Per step EGR3: install a tachometer, disconnect the IAC solenoid (9F715) connector, remove and plug the vacuum supply hose from the EGR valve nipple, idle in NEUTRAL, then slowly apply 5-10 inches of vacuum to the EGR valve nipple with a hand vacuum pump. If idle speed drops more than 100 rpm with vacuum applied and returns to normal (±25 rpm) when removed, the EGR valve is OK.
How much vacuum should the EGR valve see at idle?: With the EGR vacuum supply disconnected at the valve, the vacuum signal should be less than 3.4 kPa (1.0 in-Hg) at idle. The EVR solenoid has a constant internal leak, so a small vacuum signal is normal.
What should I do if the EGR valve fails the vacuum function test?: Inspect the EGR valve for blockage or contamination, clean it using Rotunda 021-80056 EGR valve cleaner, inspect the valve for vacuum leakage, and replace it if necessary.
What if the engine won't idle with the 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.
What tools does the EGR functional test require?: A tachometer (Rotunda 059-00010 or equivalent) and a hand vacuum pump (Rotunda 021-00014 or equivalent); Rotunda 021-80056 EGR valve cleaner is used if the valve is contaminated.