The valve itself is the first thing I checked. The valve was clean, the diaphragm worked when I sucked on it, the passageway into the surge tank from the outside looked clean, the engine stumbles when you activate the valve at idle, the tubes from the EGR transducer to the exhaust are not blocked since I can blow through them fairly easily
Then it sounds like either a vacuum leak from EVR (EGR Vacuum Regulator) or the EVR itself.
Probe the wires with a test light. One will be brite and one will be dim. if there is no dim light, then the EVR is open (blown). If you probe the dim wire while the engine is running, it should stumble the engine. If it doesn't, you've found your problem.
The EGR is a feedback system. The computer controls the EGR by regulating the vacuum via the EVR. Then it watches the DPFE to make sure it happened. Assuming the DPFE is working (even though it's been replaced) it should be able to register voltage change with EGR flow. The first thing I do when I diagnose a system like this, is to hook up my NGS scanner and check the voltage and % ratio of the EGR system. At idle, the EVR should be a 0% and DPFE around 0.6v. As you brake torque the engine a little, the EVR should go up to 30% and the DPFE voltage should go to 2-3v.
That's the first thing to do when properly diagnosing the system. After that, go point to point and make sure the EVR has vacuum and can regulate it to the valve. The valve can be working as programmed, but if the computer can't see it, it's still gonna set the code.
This is what I mean by proper diagnosis. Know the system and how it works. Then be able to pinpoint the problem without shotgun repairs.
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Atlanta Georgia (770) 949-7191