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Questions about EGR

I have a 1993 Ford Ranger with 230,000 miles. Recently the truck has developed a bad idle and a strong shudder at highway speeds. I took it to Schuck’s and used their OBDI code reader. I got a Insufficient EGR Flow code. So I switched out the EGR Valve and reset the codes, the symptoms still exist and the engine code is still being set. I have read around and noticed a lot of people discussing that on Ford trucks, it is common for the issue to be with the EGR Sensor and not the valve. Before I drop another 60 dollars I have a few questions.



Would a bad sensor cause the symptoms I have? I understand that the sensor can send false codes to the computer, which would make me think that perhaps there is no issue with the actual recirculation of exhaust gas, but rather with just a faulty sensor.



Would a bad EGR flow really cause the symptoms I have at all? I have read of others with similar issues, but nothing conclusive as to whether or not EGR was the culprit.



Thanks!

The EGR code may be generated by a vacuum leak. Make sure all the vacuum hoses are connected and the intake manifold gasket is sealed. If there is a vacuum leak, that would also account for the bad idle.
You could try a little propane around the intake gasket connection to see if the idle smooths out. Be careful if you decide to use the propane test.

The DPFE sensor could cause this code. But so can a defective EGR vacuum control solenoid.

Tester

I also notice a strong exhaust smell in the cab which is new, as well as an exhaust smell around the engine.

Would either of those account for the symptoms in addition to the error code? I assume the vacuum control solenoid would cause the symptoms, but what about the DPFE?

Yes, either could account for the symptoms. The DPFE sensor tells the ECU when the EGR valve is opened and how much. An erroneous signal can affect idle and cruising.

I’m pretty sure you can also get this just from carbon clogged passages. Did you clean everything out really well when the new EGR went on?

Aside from that problems with Ford’s DPFE sensor are somewhat legendary. A repair manual should tell you how to test components - $20 for Haynes or Chilton’s or Autozone’s online stuff might have it.

This article may help: http://www.ford-trucks.com/forums/342419-how-to-test-your-dpfe-sensor.html

For EGR low flow, on these older Fords, you must REPLACE the rather small tube that feeds exhaust into the EGR valve…It’s a nasty job…

This seldom causes drivability problems…

I changed the DPFE Sensor and reset engine code. Still getting the symptoms and still getting the engine code. This is KOER 332, so I am thinking it is just carbon-ey. Any suggestions for cleaning?