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2000 Lincoln Towncar P0401

I have an evil P0401 (Insufficient air flow to the EGR) code that will not go away.

I had this code two years ago and read that 99% of the time with these motors it is the DPFE sensor. I changed that sensor and it fixed the problem right away. So when the code came back 18 months later I just chalked it up to cheap internet parts and replaced the DPFE again, but the code came back.

None of the parts are that expensive so what the hell, I changed the EGR valve and gasket. Code returned.

I changed the EGR Solenoid, code returned.

I discovered a hole in the vacuum tubing that runs from the EGR valve to the solenoid to the block. Ah ha! Replaced that (after a trip to the junk yard - obsolete part) and the damn code still returned.

So then I tried different combinations of my new parts / old parts just in case one of the new parts was faulty. No luck.

I know that another common issue cited for this code are clogged intake passages, but I’m wondering if that true for post '97 models? Here is the bottom of the intake elbow from a '95 where you can clearly see the egr passages:

But on the '00 those passages seem to have been removed or changed:

Any advice is appreciated, I’m wondering if it’s worth pulling the throttle body off or not. The only other thing I can think of is to remove the EGR Tube to see if it is clogged. It looks rusted as hell where it connects to the exhaust so I’m sure that will be fun.

Try cleaning passages in throttle body first. This is fairly common cause for P0401 on these Fords.

I’ve found plugged EGR tubes to cause this code.

Between the two pressure taps of the tube is an orifice. This orifice gets plugged with carbon causing the code.

I’ve had good luck spraying brake parts cleaner down the tube to remove carbon from the orifice.


I’ve had good luck spraying brake parts cleaner down the tube to remove carbon from the orifice.

Thanks Tester, I’ll give this a try. Do you mean to detach the tube from the EGR valve and spray the brake cleaner down the tube there, or try to spray it down the small lines that go from the DPFE to the tube?

Remove the EGR valve from the tube and spray the brake clear down the tube.