1999 Mercury Cougar in awesome shape no engine problems, and has just under 86000 miles. I bought it recently and the check engine light came on out of nowhere and I realized It was an EGR issue the code was p0401 insufficient flow. I had a mechanic replace the solenoid valve as well as clean all of the carbon gunk off the valve and the light was off, then suddenly POPPED back on, making me really nervous and kind of upset. So today I had a few errands to run and I said I wasn't going to go get it read again until tomorrow, and it just Went off. So Is the car just very sensitive to things and is that why it goes on and off? Or is something wrong? I'm a student who really wants to keep this car nice like I bought it.
Ford vehicles commonly have this problem. Their is a sensor that determines the flow of the EGR. This sensor is called Differential Pressure Feedback Sensor or (DPFE). originally the cougar's came with a plastic DPFE they became brittle from the high engine bay temperatures. There was a newer revised part that is now metal to withstand high heat. 86k miles is roughly when you see them go bad. 9 times out of 10 on a ford the sensor is bad not the ExhaustGasRecirculation Valve. I say replace the sensor, or pay to have it diagnosed properly. And a loose gas cap will give you a gross evap leak code not a egr code.
The EGR= exhaust gas recirculation valve is a controlling device to allow inert gas into the engine at cruise. The tube below it supplies the gases and the valve directs it into the engine. Any where within this assembly carbon can build up and get lodged in the pintle of the EGR valve. Some times it is the valve and a vacuum test of the diaphragm will detect failure. Keep in mind that there are two versions of the EGR valve Positive and negative pack pressure and the test is different for a positive back pressure style valve. A flexible spring rod with a scraping device at the end wil really help in the cleaning of the tube and passages. Don't give up , your on the right road.
believe it or not a gas cap being too loose can make many check engine lights come on. Make sure you get it tight when you fill it. Make it click click click That could give that kind of code too, because the fuel system needs to be pressurized. If it isnt, you get a weird code.
