Air fuel control derate?

[Rawze]

(04-26-2022 )CSteffler Wrote:  ...
my 08 t800 with an isx600
...
cleaned the timing and metering solenoids and swapped them from front to back
...

This is most likely a CM871 engine. You did not mention what engine you had.

The engine will usually only rev up when it is getting fuel that it is not supposed to be getting. You say the ecm was replaced, it may or may not have fixed this issue in your particular case, but most of the time, when the engine revs up like that on its own .. especially only when cold ... it is typically a metering actuator issue. At least that is what it is most of the time when a CM870 or CM871 revs like you described.

(suspect metering actuator rev-up problem)...
- Watch the live fuel flow (mg/stroke) in insite or Calterm after starting it up. If the fuel flow drops off to zero as the engine revs up on its own then it has a bad/failing metering actuator(s). Swapping actuators around is not going to reveal this, and it also shows that a mechanic that who would do this likely does not know how much about troubleshoot the fuel system on the ISX very well.

When the engine revs up on its own like that, someone needs to start by checking if there is a leaky injector first. A leaky injector is a major cause of the metering (and sometimes the timing) actuators to go bad. Doing a proper injector leak test is the first step towards checking why an actuator(s) has started acting up/going bad...

CM870/871 injector leak test: http://rawze.com/forums/showthread.php?t...8#pid67948

Cure whatever leaky injector issue it may have FIRST.

But As well, the actuators need inspecting. Pull them apart... clean them well, and inspect them for excess play and step wear. THAT is the proper way instead of blind-man guessing at them like a fool.
ref: http://rawze.com/forums/showthread.php?t...8#pid67948


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A power loss issue may or may not be related to this.. It may be a completely separate issue, but the CM871's also have a known bug in the software, where they will derate (and limit fuel) and not show it. This bug that has always been in them is also related to the metering/timing actuators. What happens is that on power-up the ecm fails an actuator due to improper resistance on a coil(s), but uppon a second system check.. it passes them because maybe they are right on the edge of failing it?... who knows.. . Now the problem is that the fuel system derates the engine to protect itself, but does not show any codes, or report any derate, etc.. because the condition is now considered "good" after the second check. The derate gets hung up in memory and never gets cleared, nor reported.


Someone can use the Calterm software (and a proper monitoring screen/view) to see what the engine is doing, and you will know exactly what, if anything (like the derate described above, fuel being limited in some way, what engine operating mode it is using, etc.), that might be holding the engine away from full power/torque on a test drive.

It is a simple matter of checking exactly what that ECM is doing/commanding at any given moment. ref: http://rawze.com/forums/showthread.php?t...3#pid58693

If that engine is not producing full power/torque for any reason whatsoever.. that screen file mentioned above will show it.. and why.

Also, if this engine is de-mandated (deleted) then this known bug should not exist in the program any more .. That is, unless you have one of those 90%+ that these clowns always use, trash-can, garbage programs that some moron got off those auto-tuning sites, that most delete shops always use. Those bad delete programs will make the engine seem to run fine to the truck owners.. but internally, they severely shorten engine life, are full of software bugs, or sometimes, like you described, have mysterious power losses after service work is done.. and all sorts of other half-baked garbage.

so .. if that engine is deleted... then priority #1 would to also copy the program out of that ecm and e-mail it to me for a proper review.. not only to ensure it is not harmful to the engine .. but to also check to see if it has that software bug in it.

just my thoughts on it any ways.