Is there anyway to make sure the throttle plate is wide open all the time?
1. Disable (disconnect) any electronic throttle adjustment if the plate is held wide-open by a spring. This would likely give you a CEL on the instrument panel.
2. Remove the throttle plate if it's attached to an actuator with screws or some other fastener. This *MIGHT* give you a CEL if there is some other engine sensors that detect things are going wrong. If the only input to the ECU is a throttle position sensor, it might not trigger a CEL.
3. Aftermarket tuning for the engine.
If this engine is like other diesel engines, the throttle plate is also there for shutdown of the engine. To prevent something that a more than typical shuddering of the engine when it shuts down, some diesel engines snap the throttle plate closed so the pistons are fighting against vacuum to quickly stop the engine.
2014 Cruze Diesel - White 140,000 km
1998 XJ 3" 31" Hakka LT 350,000 km
1998 XJ 3" 31" Hakka LT 320,000 km
If the EGR valve were unplugged, what is the worst outcome? If it's just a CEL on the instrument cluster and basically nothing else, I don't have a problem with that.
I'm obviously not an engine designer, but why haven't modern diesel engines been changed to take exhaust gases from after the DPF? It seems like it would be better/easier to take clean, soot-free exhaust gases from after the DPF and put them into the intake right before the turbocharger.
I ask because a friend of mine has a Jeep Liberty with the CRD engine. That is over a decade ago, so different emissions system and no DPF. Still, the fix for those engines is to wire the EGR valve with a switch in the cab. When you start the vehicle you leave EGR on for 30-45 seconds and that is apparently the length of time the ECU checks for EGR function. After that you can flip the switch to turn off EGR and nothing happens (no CEL). You save all the soot from going into your intake and your fuel economy jumps by 10-15%.