Engine/Transmission (1998.5 - 2002) High idle/ 3cyl. idle question

[SHobbs]

Ok I got a chance to experience the high idle while in Co, bad fuel or my reserve tank was dirty and a plugged filter kept me from witnessing the 3 cyl. idle on the coldest morning. Had to use the go pedal to get it started after a filter change so no 3 cyl. I know the high idle kicks in around 32* and the 3 cyl. kicks in somewhere in the teens maybe low 20's. Can these temps be changed? Say high idle around 45 and 3 cyl. at around 32*. reason I ask is due to the fact that here in Texas it does not get that cold.



If this has been mentioned before my apologies but do you know how many threads there are about Smarty? Lots of reading.

 

[PC12Driver]

Unfortunately they're non-adjustable.



The 3-cylinder and high idle programs are activated at whatever temp the IAT sees at key-on (15* for 3-cyl and 32* for high idle). Once activated, they're enabled until the next power cycle. So even if you blipped the throttle during start, if the conditions listed in TSB 18-019-01 are met again, the RPM will ramp back up and the cylinders may drop back out.



For example, I started my truck at work and the block temp was 12*. It ramped up to high idle and dropped out the 3 cylinders. The block temp got to 70*, I stepped on the brake to return to normal idle, and then drove down the road to get fuel. At the gas station, the block temp was up to 100*. About 30 seconds after I parked the truck it went back into the 3-cylinder high idle, because even though the intake temps would have been well above 15*, that was the program that was enabled at key-on.



It's a nice system when it works, but like you suggest, it would be nice to have it kick on at a little higher temp (or based on actual outside temperatures).

 

[HBarlow]

SHobbs: Even though the automatic fast idle and three cylinder idle modes are preprogrammed by the software you can always activate the fast idle at any temperature you wish if you've had your dealer enable the fast idle mode. Well, not that I wrote that, I'm not sure the 2003 Cummins had the fast idle feature. Does your 2003 Cummins have the fast idle capability using the cruise control buttons like my former '06 did?


PC12Driver: Your post above was informative. I didn't know about the three cylinder idle at extreme low temps and your description was very clear.

 

[Erska]

This is just a thought, but maybe it can enabled, if you do a resistor with a switch there? In that temperature the IAT send a somekind of resistance, maybe if you add a solid resistor with a swtich on the IAT sensor wires, you can enable it when ever you want just a turning the swtich?

 

[SHobbs]

I was thinking that Marco might be able to make it happen through the Smarty programming.