I found a video on Youtube from someone demonstrating an easy way of checking for a faulty EGR valve. His valve had a faulty vacuum diaphragm and he demonstrated a way of testing by forcing the valve open and then closing the inlet pipe using his finger. When released to let the valve close then if the diaphragm was good the valve would stay open and, if not, it would close.
Although there was certainly evidence of my EGR working many of the symptoms still pointed to this rather than the MAF meter,as diagnosed by the garage diagnostic system, and subsequently replaced with no effect. I therefore tried sucking the inlet pipe and noted a flow of air.
Next, I tried the above YouTube test and a partial vacuum was held but the valve did close. I then decided to block the small vent hole in the diaphragm body to see if this made a difference when driven. The theory being that this would stop the flow of air whilst still allowing partial operation of the valve. (I used bluetack to cove the hole).
The road test resulted in a marked improvement. The old car, the one I'd almost forgotten, was back. Smooth acceleration. No hesitation. Reduced knock. More power. However, as expected some symptoms were still noticeable.
With this drastic improvement it has to be the EGR valve. Let's hope that the £100+ for a new valve will be the solution.
