2002 Windstar with P0401

[jeffh35]

My engine has been giving me some strange behavior and my Check-Engine Light came on. It was intermittent at first, now it stays on. The engine will "lug" sometimes when I'm driving and the car will vibrate. I thought it was a transmission problem but had that checked earlier and it was ok.

I got the code, and it's P0401. I've been reading about it all over the web. It's the EGR system low/no flow error. From the behavior I think it may actually be the EGR valve, but I need to get a vacuum pump to test it.

Most posts point to the DPFE sensor since it seems to go bad the most, but the 2002 has a small plastic one instead of the aluminum housing. If it was just this sensor I would assume nothing else would be wrong. Of course, the shimmy could be something unrelated but since they happened near one another I am suspecting it is causing it.

I hate to spend $30 on the sensor and $55 on the valve if it's not going to fix it. Just wondering if anyone else has had this problem? Any insight on whether the vibration is due to the EGR problem? Any diagnostics I should run other than those in the Haynes manual (voltage, vacuum...) ?

Thanks.

[DRW1000]

The EGR valve opens when the engine is warm and at relatively high RPMs (I think about 2500 and up). This valve routes some exhaust gases into the intake stream and lowers the combustion temperatures and thus reduces NOx production.

If you are getting P0401 then the PCM "knows" it has commanded the valve open but the feedback from the DPFE indicates that there is low flow.

This could be caused by the EGR vacuum regulator (solenoid?), the EGR valve itself, the DPFE or even clogged ports.

One easy way to check the valve operation and the ports is to place a hose on the EGR valve vacuum line (disconnect the one already there and plug with a golf tee). Whith the engine idling gently apply vacuum to this line via a vacuum pump or mouth power. If your EGR is working it will stall the engine. If some of your EGR ports are clogged then usually you will have a misfire (different codes) on the least clogged port's cylinders.

You can test the DPFE by using the same technique while measuring the voltage from the DPFE (backprobing). You will notice the voltage is proportional to the amount of vacuum applied.

If these items seem to be okay then the problem may be with a clogged vacuum line or the vacuum controller itself.

None of these should cause strange behaviours unless a misfire code appears too. An inoperative EGR system should give the code you mentioned but I don't believe the van will run differently.

[12Ounce]

If the problem is now "staying on", I would suggest removing and plugging the vacuum control hose that connects to the EGR valve itself.

Now, do a test drive. If you still have a lugging problem ... it is not caused by EGR feedback... unless the EGR valve is stuck open (a rarity).