With a normal operating EGR system, the throttle control valve is partially closed at idle to restrict air flow, which creates draw from the EGR valve.

When a true EGR delete has been achieved, the throttle control valve is now wide open, with no restriction to the intake. Therefore, running freely.

Upon shutdown of the engine, this throttle control valve is what closes off 100% to strangle the motor (i.e. stop the motor). So when it is already partially closed, the engine is already not running to its best efficiency, so it is quite easy to stop i.e. a softer close as it is already partially closed. When the throttle control is fully open, it is more of a dramatic shut-off, as the motor has full flow at idle and then is suddenly closed completely when the ignition is turned off.

Some people have concerns with this sudden movement in the engine, but if you think about it, the engine moves much further through torque, through gear change and heavy acceleration than when this shut down occurs.

Feedback we have received is that this is more noticeable on the manual vehicles as they have dual mass fly wheel system.

Why is the throttle control valve important, and why you shouldn't 'mess with it'.

The EGR Delete Module does not 'mess' with the throttle control valve. When driving in extreme cold environments, the EGR system does not operate. This is how the EGR Delete Module works, it tells the ECU ambient air temperature is a certain degree, meaning the ECU tells the EGR System to remain dormant (this air temp gauge is NOT used for fuel ratios in the models these modules are available for). Therefore, when driving in these cold environments, you can experience a 'rough shutdown'.

Some people drill out or remove the valve from the throttle control system when an EGR blanking plate is put in or a 'home made' delete is done. This is extremely dangerous as the valve is what closes to shut down the engine, and without this valve, or with holes it in, you have lost the one thing that can prevent a runaway diesel. This is a rare thing to happen, but I suggest you google it to see how important the valve really is.