My truck is a 02' 6sp manual 24v H.O. Every now and then coming up to a stop light I push the clutch in and it seems to run a high idle for a few seconds before droping down to normal. Only does this once in a while. It's only about 100-150rpms diff.
Another thing that drives me nuts is when its cold out right after start up the lights come on bright and then go dim? (rpm fluctuates) I know there is a "high idle"on this thing but is it supposed to stay steady? Or fluctuate?

Thanks DOG

 

Not too sure about the idle increase....

As for the dimming of the lights, isnt that your air heater grids cycling on and off?? They draw a lot of current when its cold out, which in turn dims your lights. Watch your voltage indicator....u should see it fluctuate as well.

 

Dog,

I may be way off here but your lights shouldn't change with your RPM's. After initial startup everything runs on the alternator which rectifies an abundance of A.C. to D.C. currant. The only time the lights should dim is when you shut down or there is a hefty drain on the charging system...very hefty.

I wonder if your small idle fluctuation could be caused by a bad bearing somewhere...or a shorted componet.

Just something to think about.....

 

The fluctuations in voltage (results like dimming lights, different idle etc) are caused by the grid heaters. The grid heaters will heat up intake air as long as it's a: cold enough, and b: below 15 mph speed. Since the heaters do draw a hefty current (like 70A) they lead to a fluctuation in voltage and the idle will sound different and be a tad lower than without them on. The intake heaters will eat up about 1.something horsepowers from the crankshaft. Engine idle speed is controlled by the ECM and the ECM will listen to demands for higher idle from the PCM too- the PCM controls charging circuit, A/C, PTO and a whole lot of other gizmos. I don't know for shure on the manual CTD but on some of the diesels over here we do have a kind of "dash pot" in the software. This is intended to improve driveability to avoid stalling the engine when the computer expects you to let the truck creep a bit forward on the clutch with the accelerator at idle.

HTH

AlpineRAM

 

I did not think of the grid heaters running after start up, makes sense though.
But after it is warmed up (i.e. 80mph for a hour and ten minutes ;D) I pull up to the first light off the freeway and after I am at a stop sometimes it will remain on "high idle" for about 3-5 sec's then drop down to normal idle and be fine. This only happens every once in a while.
Thanks for the other ? anwsered 8)

 

The grid heaters will continue until a predetermined heat is reached.
This will, indeed, lower the rpms and dim the lights.

I place a stick between the go peddle and the seat post to increase the rpm's to about 800.
I noticed that if I hold the rpms above 1000, the grid heaters wont shut off. :-

I dont have an answer for your rpm fluctuation after the truck warms up. ???
Have you tried to reset your APPS?

Rich