Engine/Transmission (1998.5 - 2002) 1000 RPM after start up cold

[ntillm01]

While waiting for the grids to finish cycling yesterday, I flipped the sunvisor down and read the starting instructions. They stated that below 70 degrees F, it is considered a cold start and the following steps should be used to cold start the engine. Turn the key on, wait for the wait-to-start light to go off, start the engine. Then, raise engine RPM to 1000, and let it back to idle.



So I did this the last couple of cold starts. Bringing it up to 1000 RPM seems to kick both grid heaters in full and the engine seems to be working harder. This lasts about 5 seconds, then the heaters go off and I let in back to idle. I'm not sure if this sets the engine controls up for a faster warm-up or not, but it seems to be happier when I do this.



My question is: Does anyone know if this makes a significant difference over simply cranking and letting it idle?

 

[B.G. Smith]

I think it just clears out any unburned fuel and makes the engine run smoother/quicker when it is really cold. The engine won't warm up to normal temp if left idling below 1000 rpm. bg

 

[HoleshotHolset]

[BRAIN DUMP]

This sounds like the diesel equivalent of what almost all fuel injected gassers used to do... .



Remember back when you started up an old fuel injected gasser..... GM's TBI system comes to mind... . and it would immediately go to 1200+rpm for about 5 seconds and immediately return to idle?



In fact - if you sit and think about it... . pretty much all gassers without any type of MAF (speed density systems) do the same thing... . Methinks the ECM is hard pressed to figure out the correct mix without airflow data... . and the first few seconds of a cold start are critical... . so they may as well crank up the RPM's to get her settled into a good idle before you cram it in gear and take off... .



With the suggestion on the visor - Cummins is admitting that the ISB could run rough for a little bit right after you crank it over when it's stone cold... . and instead of automatically raising the RPM's - they let the operator decide if this is necessary. Imagine someone cramming their stone cold ISB into 'drive' while it's stone cold AND idling at 1200rpm?



The choice was made, and Cummins decided that it's better to let people decide to ramp up the idle themselves than to break input shafts... . although with 'torque management' this would probably be reduced a bit... .



Matt

[/BRAIN DUMP]