EGR Valve Can Block Or Fail An Cause Running Faults but what do they actaully do ?
EGR valve (Exhaust Gas Recirculation) directs a small amount of exhaust gases back into the inlet air charge, and this lowers the maximum temperature of the burning fuel.
The valve ensures the EGR system is disabled/ closed at idle, when it would otherwise lead to erratic idling, and at peak power, when adding exhaust
gases would reduce power output and creat a boost leak.
Because exhaust gases are pumped into the engine this valve is very likely to clog up and stick and become coked up on some applications and start to malfunction intermittantly and then permanantly.
This can have a significant effect on the performance of the turbocharger as its trying to compensate for boost leaking past what should be a closed valve…this in turn causes the turbo to over spped which you can read about in one of our other sections on route causes for turbo failiure. It is important to check the valve is functioning correctly.
So what will happen if my EGR becomes faulty ?
A faulty EGR valve can result in excessive carbon/soot at the turbine end of the turbo charger. This could cause the VNT mechanism to become clogged and stick which in many cases will cause engine management lights to appears along with reduced performance known as “limp mode”.
Excessive production of nitrogen oxide
Smoking at idle and low rpm
Erratic idling or unable to idle
Poor operation when cold
Increased fuel consumption
Lack of performance
Fault light and/or fault code activated
Possible reasons why the Valve does not open
EGR valve sticks/gummed up
Air leak on the vacuum side
Vacuum connections disconnected leaking or incorrect
Faulty electric switch pressure converter valve Non-opening blow-off valve (dump vale)
Possible reasons why the Valve does not close
Heavy carbon deposits on egr valve tappet or valve
EGR valve damaged through overheating due to:
Incorrect control of egr valve
High exhaust back pressure – Blocked dpf or cat or collapsed exhaust baffles
Failed dump valve
Air flow meter or other sensor signal faulty
Intake pipe in the EGR system partly constricted by deposits or blocked
Oil leak from turbocharger causing carbon build up – please see blocked dpf