MEgearhead
Veteran Member
I have been trying to figure out a rough idle issue for a while now. I recently replaced the turbo and cam. Neither are BHW parts. The turbo is a GT1756 hybrid and the cam is a higher lift/duration BEW.
What happens is after cruising down the road when you disengage the clutch the engine coasts down up to 200 rpm low and runs rough for 15-20 seconds, then recovers.
I have changed the fuel filter and verified there are no leaks. We also ran some diesel purge as the idle stabilization values were spread out considerably. Setting the torsion value at -2.0, 0.0, and +2.0 has no perceivable effect.
After logging several different values the only thing I can find that directly correlates is start of ignition timing. When it is idiling rough the start of ignition is over 3 deg. BTDC. The more advanced the worse it is. After several seconds the timing ramps down to below 2 deg. BTDC and then the engine smooths out and rpm raises up to normal.
What's also interesting is that often EGR and N75 are off while it's running rough then N75 goes to full, and EGR starts regulating once the idle recovers. However, this doesn't always happen, but when it does it always follows the idle recovery. The change in timing always precedes the idle recovery.
I'm interested what others with a manual swap have noticed regarding idle from cruise just after disengaging the clutch.
We set the injector rocker preload with a dial indicator, but I'm tempted to take the cylinder head cover off and verify it along with overall lift of each injector lobe.
Any other thoughts?
What happens is after cruising down the road when you disengage the clutch the engine coasts down up to 200 rpm low and runs rough for 15-20 seconds, then recovers.
I have changed the fuel filter and verified there are no leaks. We also ran some diesel purge as the idle stabilization values were spread out considerably. Setting the torsion value at -2.0, 0.0, and +2.0 has no perceivable effect.
After logging several different values the only thing I can find that directly correlates is start of ignition timing. When it is idiling rough the start of ignition is over 3 deg. BTDC. The more advanced the worse it is. After several seconds the timing ramps down to below 2 deg. BTDC and then the engine smooths out and rpm raises up to normal.
What's also interesting is that often EGR and N75 are off while it's running rough then N75 goes to full, and EGR starts regulating once the idle recovers. However, this doesn't always happen, but when it does it always follows the idle recovery. The change in timing always precedes the idle recovery.
I'm interested what others with a manual swap have noticed regarding idle from cruise just after disengaging the clutch.
We set the injector rocker preload with a dial indicator, but I'm tempted to take the cylinder head cover off and verify it along with overall lift of each injector lobe.
Any other thoughts?