Engine/Transmission (1998.5 - 2002) 3-Cylinder Idle scan tool trace

[ntillm01]

For you folks interested in the 3-cylinder high idle. There has been some question as to what gets the feature to kick in, so I have been logging some data on cold start-ups this week. I am using the Alex Peper Car-Code software.



From what I can tell, it keys off of the initial IAT temperature, and not the running IAT. The traces show IAT doesn't get below 15 after it's running. I am posting the exported . csv file so you could load and graph it in a spreadsheet. If you have Car-Code software, you could playback the . dat file. I added . txt to both so they would upload.



In this trace, it was a 14 deg F cold start, no block heater. The 3-cylinder idle kicked in as soon as it reached 1200 RPM. You can see it in the RPM fluctuation... kinda neat. I let it run that way all the way until it kicked back to normal idle, which appears to happen once ECT reaches 173 deg F.

 

[Billy Diesel]

From what I can tell, it keys off of the initial IAT temperature, and not the running IAT. The traces show IAT doesn't get below 15 after it's running. I am posting the exported . csv file so you could load and graph it in a spreadsheet. If you have Car-Code software, you could playback the . dat file. I added . txt to both so they would upload.

Soooooooooo, for those of us that like to plug our trucks in, but want the 3-cylinder shut-down to heat the trucks up, it may be possible to interrupt the IAT sensor reading with a value equal to -30F outside, and it would work? And then we could switch the signal back to the sensor once the engine was started, and we wouldn't have to worry about disrupting other engine programs?



BTW, cool data!

 

[ntillm01]

Soooooooooo, for those of us that like to plug our trucks in, but want the 3-cylinder shut-down to heat the trucks up, it may be possible to interrupt the IAT sensor reading with a value equal to -30F outside, and it would work?



There you go thinking again



I really don't know, just guessing by what the ECM data is showing.

 

[Turbo Tim 1]

I would beg to differ with your findings based on my experiences. I have had my truck plugged in all night (-10F), started the truck, let it idle for a while and everything stayed normal, drove 2-3 miles to the store, left the truck running, came out and the 3 cylinder idle had kicked in. I've also had really cold days (-22F) without the truck plugged in where it will go to 1200 rpm and three cylinder idle immediately after being started. Other times you can watch it and the ramp up in rpm's won't start until after the grid heaters kick off. From what I've seen, if you've had the block heater plugged in, the area around the IAT stays warm enough not to allow the high idle to work unless it's really cold and you drive down the road and pull in some really cold air, enough to chill the sensor and it's surroundings. Maybe I am completely wrong, maybe it uses the initial temp and then if the temp drops below that it will work based on that. Keep putting out your information, if we could really nail this down we could make up something like Billy Diesel is talking about.

 

[Billy Diesel]

Only when it got below -40F did I ever get the high idle function after having the truck plugged in all night. I never did get the 3-cylinder.



Before the homemade high idle, I would fire the truck up and start driving (easy) almost immediately. Even when it was -30F and I had less than a 5 mile trip, I couldn't get the high idle. That was back when I used the "stick-on-the-pedal" high idle... .

 

[ntillm01]

With the block heater, it has to be pulling in really cold air to activate the high idle. I did a trace of that too. Overnight low of 6 deg F, then start up in the morning. The ECT and IAT both were at 95 F. Start the truck and the lowest IAT got was 45 F after the grid heaters were off for a while.



Finding out how it works is exactly why I started capturing the data. It very well could be it will kick in based on the lowest IAT it's seen, whether it happens on key-up or after that. Start-up from sitting still may be slightly above the high-idle range, then a drive down the street pulls IAT down enough for it to engage. I'll post the interesting logs I get and we might figure more out. Glad this is usefull.

 

[Froadin]

I just recently got this flash done while in OR, and it was just warm enough not to kick in. I would definitely be interested in finding a way to fool the computer into kicking this on when I want it to.

 

[Andy Redmond]

If it doesn't upset other circuits and functions, what about someone measuring IAT resistance when the high idle feature works (sounds like frigid temps with no block heater) and then overlaying a harness with an in line resister with (many or few ohms) to replicate the measurement taken previously. This switched circuit could then be controlled with a switch to "force" a reading to the IAT and thus a manual control of the high idle?



Perhaps the aftermarket will make some sort of an adjust. black box with a curcuit board, that will allow for high idle and still allow some of the oems software to control function (override) manual control with conditions (not at road speed or in gear, etc. etc. )



Good luck

Andy

 

[Froadin]

I would think it should be a very simple thing to have a second switchable circuit to activate it. And you only need it to be on the other circuit until it actually kicks in.

 

[Billy Diesel]

Perhaps the aftermarket will make some sort of an adjust. black box with a curcuit board, that will allow for high idle and still allow some of the oems software to control function (override) manual control with conditions (not at road speed or in gear, etc. etc. )



Good luck

Andy

I believe that PS has a box like that... . I don't know if it is speed / gear sensitive though... .



--

-Will

 

[GKinney]

my data

Ok here is what I have been seeing on my truck. This morning it was around -5*F here, truck was plugged into timed outlet which runs for a little over 2hrs. After un-plugging truck and then starting it up, the high idle kicked in followed by the 3cyl. shut down. I have seen it not kick in the 3cyl. , only the high idle, when the temp was 14*F. with it not plugged in. The truck always sits at least 16hrs after it is shut down the day before. Must be the sensitivity of the IAT sensors vary from engine to engine, or mine is dirty?? Anyway, impressive info... . ntillm01 keep up the good work. Thanks gary

 

[Turbo Tim 1]

Just some more info, plugged my truck in last night at 5pm, it was -25F when I went out at 8:30am to start it. Truck started and after the grid heaters stopped it went to 1200 rpm but the 3 cylinder did not kick in. Wish I had a lap top and the software to see what was going on!

 

[Froadin]

Try cleaning your IAT sensor and see how it works the next day.

 

[Andy Redmond]

I think you were looking for low cost but here's a plug n play solution about $485 msrp. .



http://www.bd-power.com/ram/product.php?pn=High Idle Kit&tt=ram

 

[Froadin]

Too much $ when I would only really want/use it for cold startups. Of course this is great for other people needing the high idle for other stuff though.

 

[SnoKing]

The temp sensor under the drivers battery is suppost to be the one that reads the temp to start the high idle, but this says IMT. Is IMT measured with the IAT sensor or the one under the battery?



Cold idle engine warming.

This bulletin involves selectively erasing and reprogramming the Engine Control Module with new software. This bulletin applies to all Ram trucks built after December 17, 1997 equipped with the 24-valve 5. 9L Cummins diesel engine.



Extended idle operation, especially in cold weather, can allow varnishes/oils to condense on the exhaust valve stems, leading to stuck valves, and damaged valve train components. The repair procedure involves calibration software that will activate when certain parameters are met, reducing the chance of valve sticking as well as improving cab heat warm-up time. Idle speed will slowly ramp up from 800 rpm to 1200 rpm when all of the following conditions are met:

* Intake Manifold Temperature less than 60°C (32°F)

* Coolant Temp is less than 60°C (140°F)

* The transmission is in Neutral or Park

* The Service Brake pedal is not depressed

* Throttle = 0%

* Vehicle Speed = 0 mph



If intake manifold temperature (IMT) is less than -9°C (15°F), three of the cylinders will be shut off upon reaching 1200 rpm, creating a slight change in engine sound which is normal. Thus the engine has to work to overcome the three “dead” cylinders. This allows the engine to create increased heat in the cooling system, allowing more rapid warm up.



Either feature will abort when any one of the following occurs:

* The automatic transmission is placed in gear (forward or reverse)

* The service brake pedal is depressed

* Throttle position is greater than 0%

* Vehicle speed greater than 0 mph

* Coolant temperature is greater than 79°C (175°F)

SNOKING

 

[Froadin]

Ok, what is the value that the computer wants to see for the high idle, and for the 3 cylinder? The software your using should show those values right?

 

[Turbo Tim 1]

Manifold temp and IAT are one in the same. The IAT is the device used for the high idle function. This is the reason why the high idle normally won't function if the truck has been plugged in.

 

[SnoKing]

There is not reason why high idle will not restart in a running engine, if you meet these requirements again:

* Intake Manifold Temperature less than 60°C (32°F)

* Coolant Temp is less than 60°C (140°F)

* The transmission is in Neutral or Park

* The Service Brake pedal is not depressed

* Throttle = 0%

* Vehicle Speed = 0 mph



So a truck parked in really cold weather idling will cycle in and out of the feature if it get to 175 degrees coolant, and then cools to less than 140 and IMT is below 32 degrees. repeat! repeat! It could also go in and out of 3 cylinder mode most likely.





I have started mine at a motel in Cle Elum in Eastern Washington, had it high idle and three cylinder, driven across the street to fuel the snowmobiles leaving the truck running and it has gone back into both. SNOKING

 

[Turbo Tim 1]

Absolutely a true statement as has been said in this thread. Mine does it often when I leave for work and stop at the corner store 3-4 miles from the house both high idle and the 3 cyl thing. I've seen the high idle kick back in after being up to full temp and back but never the 3 cylinder idle..... why..... maybe it doesn't get cold enough at the IAT after having been to 175 degrees.