within the last 4 months i had my EGR valved replaced. However, my engine light came on again the next day. I took the car back to the mechanic three times, but they claim the EGR valve is working properly. I decided to get a second opinion. The second opinion cost me $609. The new mechanic claimed I needed a computer board and that would fix the problem. Yet again, the engine light came on. Took the car back to the second mechanic, the said the EGR was working properly. The mechanic said he replaced my PCV valves. Fortunately this time, I did not have to pay more money. Anyway, I took the car to the emissions facility in my state and the system said "Fault Codes: P0400 EGR Flow Malfunction". If anyone can assist me with how to fix this problem, that would be great.

THANKS!

 

EGR valve working is one thing and EGR flow is another. If the mechanics are checking operation of the valve then it may be true that it is working; however, you may have no flow. The flow path from the EGR valve to the intake manifold (IM) often gets plugged up with carbon. This flow path is part of the intake manifold and it opens into the IM just behind the throttle body. If you look carefully inside the IM, you'll see two hole or bumps at the bottom of the IM. If they are plugged clear them.

Before you get into all of the above, one way to test the for EGR flow is to apply vacuum to the EGR valve while the car is idling. If the flow path is open then the car will idle rough and/or shutoff. If this test passes then you might want to make sure that vacuum is being received by the EGR Boost sensor.