EGR valve (too much flow)

The mechanic I've been taking my Golf TDI too found an egr error code (egr clogged, manifold system needs cleaning, etc). He cleaned it seemingly and now the error code is saying that instead of "insufficient flow" that there is "too much flow". Even though the car is running better than ever, the check engine light is coming on again. Can anybody help? Thanks in advance.

Matt

VW 2000 Golf TDI GLS

EGR excessive flow trouble code almost always means the EGR valve is bad (diaphragm ruptured so it doesn't seal vacuum and the valve never opens.) Easily checked by a mityvac. But this code can also be triggered if the vacuum never makes it to the egr valve. (vacuum hose or vacuum solenoid, or weak vacuum pump)

Lots of confusion with this code because most folks logic would say, "if the valve doesn't open how can it have excessive flow." The answer to this is the computer cant see EGR flow. But it can see intake air flow at the maf sensor. When EGR valve opens it should see a lower maf reading as the egr gasses are now subtracting from the amount of intake gasses that are flowing into the engine. So the computer verifies EGR operation by watching Maf flow drop when egr opens. So if egr doesn't open when commanded to the computer see's "excessive" flow on the maf sensor.

Wow, Thanks Richard. Looks quite comprehensive. The mechanic working on mine said he is putting in a delay for the egr. Hope he's right. I showed him what you said and he still said he was confident this will eliminate the issue. Really appreciate the feedback. Guess I'll have to bring it out to you in Kansas City or find an appropriate mechanic if he is wrong.