HOW TO INSPECT EGR VALVE
Before attempting to troubleshoot or repair a suspected exhaust gas
recirculation (EGR) system on a vehicle, the following conditions
should be checked and be within specifications.
- Engine is mechanically sound.
- Injection system is operating properly.
- Mechanical-vacuum advance is properly adjusted or the electronic advance system is operating properly.
If one or more of these conditions is faulty or operating
incorrectly, perform the necessary tests and services to correct the
problem before servicing the EGR system.
Before attempting any tests of the EGR system, visually inspect the
condition of all vacuum hoses for kinks, bends, cracks, and
flexibility. Replace defective hoses as required. Check vacuum hose
routing. (See the underhood decal or the manufacturer's service manual
for correct routing.) Correct any misrouted hoses. If the emissions
system if fitted with an exhaust-gas-recirculation valve position (EVP)
sensor, the wires routed to it should also be checked.
If the EGR valve remains open at idle and low engine speed, the idle
operation is rough and surging occurs at low speeds. When this problem
is present, the engine may hesitate on low-speed acceleration or stall
after deceleration or after a cold start. If the EGR valve does not
open, engine detonation occurs. When a defect occurs in the EGR system,
a diagnostic trouble code (DTC) is usually set in the powertrain
control module (PCM) memory.