Thread: EGR Valve issues?

Thanks for the info guys. How does blanking off the EGR affect the warranty since I've got 2 years and 9 months left and no warranty extension, I need all I can get.

I found this about the Nissan engine on a patrol site. It might give some of you a few ideas. I hope it can help.
Nissan Patrol ZD30 Engine Problems.

These engines run relatively high boost levels and as clean diesel engines, they also use high levels of exhaust gas recirculation (EGR). This in turn reduces the amount of NOx released into the atmosphere and enables the vehicles to pass stringent emission standards.
One problem is that the high boost levels create high pressures in the crankcase which in turn pushes reasonable amounts of oil past the crankcase baffle and into the engines intake system. This oil finds its way into the intercooler and eventually into the inlet manifold, where it mixes with EGR gasses to form a thick black greasy substance that restricts the inlet manifold runners. In most cases the runners most affected are the rear ones, which are closest to the EGR valve itself.

The ZD30 engine management system relies on input signals from various engine sensors. The Engine Control Unit (ECU) determines fuel delivery (timing and duration) depending on input signals from the Mass Air Flow Sensor (MAF), Throttle Position Sensor (TPS) and engine speed. The volume of air entering the engine determines how much fuel is injected, but the ECU doesn’t monitor or have mixture control over each individual cylinder. The engine lacks an exhaust temperature sensor, so it can’t know if a particular cylinder is being over fuelled or running rich.
As a result of this and the inlet manifold restrictions mentioned above, the front cylinders can run lean and the rear cylinders rich. It’s common knowledge that over fuelling a diesel or running it rich will develop excessive heat.

Along with this, MAF sensors are known to give faulty input voltages to the ECU if they become contaminated or insulated against the cool induction air passing through them. Shutting down a hot engine will cause oil fumes to be forced up to the MAF sensor and contaminate it with oil against the normal direction of air flow. A contaminated MAF sending lower voltage signals to the ECU will usually create a lean condition, but the power loss may increase the drivers throttle input which can increase the fuel load and increase high combustion temperatures even further.
The engine does have a boost sensor, but it plays no part in fuel mixture control. The ECU will reduce boost when it gets too high, but this system is very slow to react and boost spikes of up to 25psi are common.
One of the advantages of Variable Geometry Turbochargers, is that they can be controlled electrically using vacuum rather than pressure. The ECU controls a vacuum solenoid using pulse width modulation (PWM) and by rapidly switching it at different pulse widths, it controls how much vacuum gets to the turbocharger’s actuator and in turn how much boost the turbo produces at any given rpm and load. This is very important because it enables the ECU to reduce boost at any time, even under load or when the throttle is partly pushed open.
The ECU can reduce boost to promote maximum EGR flow by reducing intake pressure while opening the EGR valve with the throttle pushed open under light load conditions. This forces more exhaust gas into the inlet manifold and combustion chambers, which in turn reduces peak combustion temperatures and NOx emissions. When this happens, EGT’s rise because there is less cool oxygen enriched air entering the combustion chambers and more hot exhaust gas, further increasing exhaust temperatures.
Any combination of the conditions mentioned above can cause an engine failure due to excessive combustion temperatures, but there are relatively easy and cheap ways of monitoring and controlling these systems. Taking some precautionary measures should reduce the chance of an engine failure or at least prolong the engine’s life.

What can be done to reduce the chance of an engine failure?

Most importantly, fit an EGT and Boost gauge to monitor what’s happening inside the engine. They won’t stop it from melting a piston, but should warn the driver of any pending issues before they become terminal.
Anything that can be done to lower EGT’s will be beneficial.
Fit an Oil/Air Separator or Catch Can to reduce the amount of crankcase blow-by oil that enters the intake system and contaminates the MAF sensor. The Mann & Hummel Pro Vent or a CKD Separator are the units of choice.
Blocking the EGR valve, although illegal in many parts of the world, does have benefits in stopping hot exhaust gasses from entering the combustion chambers and will lower EGT’s. It also reduces the chance of the inlet manifold runners becoming restricted by the thick black grease when it mixes with oil from the crankcase and helps to keep the engine oil cleaner for a longer period.







Blocking the EGR, valve will increase boost, so something has to be done to lower boost and also stop the ECU from reducing boost to promote EGR flow. The easiest and best way is to fit a Manual Boost Controller and take boost control away from the ECU. Best way to do this is by a Multi Stage TDi Dawes Controller to set two maximum selectable boost levels and a needle valve to control and set the spool up rate. This mod also stops high boost spikes and the possibility of overboosting.