Starting trouble

Robert Mueller

Asked by Apr 29, 2016 at 03:54 PM about the 1999 Ford F-150 Lariat Extended Cab LB

Question type: Maintenance & Repair

I just replaced the EGR Pressure Sensor. Now my
truck has trouble starting, but, only after it has
been off for a while. There aren't any errors on the
dash. Once it has started, it runs fine and will
restart without a problem.

1 Answer


The DPFE measures the pressure difference across the orifice and sends the result to the computer. The p0401 code is lack of or low flow on a test the computer requests at startup and once during each drive cycle. The blockage likely is in the intake manifold behind the EGR valve. All you need to do to check this is apply vacuum to the EGR valve just enough to open it. If the port is open, the motor will stumble and run rough while idling as the indication it's open.If this check failed, you would have not needed to replace the DPFE but there is always a chance the DPFE needed replacement from accumulations you found. This system has to work with contaminated exhaust at all times. Have it read for codes,AGAIN even if the check engine light is NOT on the computer will have stored information and codes. Discount auto stores will read codes for no fee. Write them down. DPFE Delta pressure feedback emission

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