What does the EGR valve do?

Exaust Gas recerculator . Allows exaust gas into the combustion chamber ,was introduced in the mid or early 80's & used to cool down cylinders & suposibly burn some unburnt fuel

Bonz have a look at this.

Click here

Baz.

I have also heard that a failure of the valve renders the vehicle stationary? Is that correct?

Hi Bonz,
Its main role is (as has been said) to reduce the temperature in the combustion chamber. This reduces nitrogen oxides emissions (NOx) which are ozone depleting gases. With emission regulations becoming tougher overseas and locally, things like EGR systems are becoming more common.
The exhaust gas recirculation is controlled by valve with a small electric motor, this motor is ECU-controlled normally.

Just a bit more imfo on your egr valve.

When polutants became an issue to people it was discovered maybe 20odd years ago that while high combustion temps lead to a greater efficiency for petrol and diesel engines ( do any of you rember l think it was isuzu , had a ceramic engine , thats cylinders, a lined combustion camber and piston top ) high flame front temps ,remembering that your fuel burns in a controled fashon it dosnt explode , produced large amounts of nox so a meathod of lowering the flame front was done by introducing an inert substance , yourexhaust gas .

Early systems in the mid to late 70s yoused vacuum of the engine to this as high revs/vacuum produced high combustion flame front temps thus lots of nox.
High vacuum would open the egr valve thus introducing the gas that would delute the incomming charge of fuel,lowering the flame front temp and reducing the emmissins of nox.

N