I have a 96 explorer 4.0 ohv with the check engine light on. A scan indicates code 401, insufficient flow detected. Mechanic replaced egr valve and cleared the code. CEL came pack on, code 401. I replaced the DPFE sensor and both hoses. Blew through both hoses to make sure there was no blockage and cleared the code. CEL came back on within 30 miles, same code. HELP!! running out of ideas. Jack
You need a better mechanic. The EGR system is simple to diagnose for anyone with a handheld vacuum pump, a scanner, basic understanding how things work and a manual. Now that you replaced the valve and the DPFE (presumably it's not connected backwards), we can assume that there is indeed insufficient flow and it is not caused by a malfunctioning valve. Still quite a few options: bad regulator (solenoid), no or low vacuum supply to the regulator, an obstruction between the regulator and the valve, clogged EGR tube (at the restriction point perhaps)... What should I say? You can keep throwing parts at it, or try to diagnose it. Your choice A very simple test to see that there is no major obstruction anywhere in the EGR path is to let the engine idle and force the valve open with a vacuum pump (or perhaps by smartly sneaking a tee into a vacuum line somewhere). When the valve opens the engine should stall, or at least hesitate severely.
Yep, new mechanic is on order!!(already figured that one out). Think i found the problem about 2 min after the post. A disconnected vacuum line to the egr valve. Thanks, Jack
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