4.6l warm weather egr problem p0401
03-13-2009, 04:22 PM
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4.6l warm weather egr problem p0401
I wonder if anyone has run into this problem. My truck is a 1998 f150 4.6 with 135k on it. When the weather is cold it will not set a check engine light. When it is over 32 degrees the light will come on after about 10-20 miles of driving. It will set both p0401 and p0401pd. I have checked the codes in the winter and the p0401pd will set but the check engine light will not be on. I have replaced the dpfe sensor and removed the egr valve to clean( it looks ok). Thank you for any help.
03-14-2009, 02:19 PM
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Stock Answer:
The stock response to your question is: Have you cleaned out the EGR ports in the intake goose-neck?P0401, I believe, is "insufficient EGR flow". If the DPFE sensor is new and the EGR valve is clean and working, then a low flow could be produced by clogged EGR ports or a faulty vacuum control valve, the other device living on the rail with the DPFE sensor.
To check for a clogged EGR port and/or a clogged edge orifice in the EGR pipe start the engine and let it run at idle; pull the vacuum line off the EGR valve; attach a vacuum device to the EGR valve vacuum port and pull a vacuum of 5-10psi on the EGR valve; the engine will run roughly or stall if the system is open and clear.
If all is clean and clear, then the vacuum control valve may be bad.
