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Rawze

When I mentioned 'fuel pressure issues' as a possible cause, here is more on that. Your descriptions actually point away from this as being an issue...

Typical fuel pressures at idle for an ISC on a de-mandated engine should be in the 490 - 530~ish bar range. On a healthy engine, they do not start to show signs of surging until its down in the 460bar or so range .. 420 being the lowest pressure it can be programmed to before it becomes a real problem. If it is set low, then how low it can go before it starts surging is highly dependent on the restrictions in the CAC/intake, and this is per vehicle .. so 520-bar is high enough and safe for everything that I have ever seen, even on poorly designed intake systems like the (garbage from the factory) highly restrictive CAC units that F750's have in them, as well as most RV's with their highly restrictive garbage CAC's on them as well. After-market CAC units make this even worse most of the time too.

This means that if your seeing 580~ish bar (8470 psi) at idle, .. then the fuel rail pressure alone is not likely be your problem at all. Your mention of it running 580-bar at idle actually sounds slightly high, not low ... and higher than normal fuel pressures at idle will NOT contribute towards surging, but the opposite .. and mostly result in causing a noisier valve-train, especially when the engine is cold instead.

as well. that turbo, and its speed sensor feedback needs to be fixed properly too. For all anyone knows, that highly likely could be the bulk reason that it is not running right. It should not be showing 150k rpm's at idle. - Has anyone even bothered to take the actuator off it and ensure it is not locking up at 100% closed.. choking the exhaust manifold off and causing all the surging, etc.. because the exhaust manifold itself cannot breathe properly?, and the controller just does not know it?.

you guessing it into oblivion is also not going to solve your issues. You need to see what that engine and its ecm is doing via calterm,.. and what is in control of that fuel state in particular while its acting up. - that will point you towards why it refuses to idle up, and will also likely point towards other issues. for all anyone knows, the engine might have jumped operating modes and is not stuck there due to one reason or another, so things need to be checked properly.

Use this CT screen file to see what is gong on. Get some desktop recording software and run the engine .. record the desktop and the data in the screen live... while its acting up, etc.. and then others can analyze the data for the fuel states, engine operating modes, etc.etc. and other things properly.
ref: http://rawze.com/forums/showthread.php?t...6#pid28636