Engine/Transmission (1998.5 - 2002) truck revs up during extended idle?

[BWillard]

OK, heres the situation. Every morning while I'm getting ready for work, I run out and start my truck (it's cold here in PA) and let it warm up. Now I know that the VP44 isn't supposed to be idled for extended peroids for lubrication purposes, but at 20 minutes of idleing on the nose it starts to rev up! It will surge up and down even up to 1500RPM on occasion. As soon as you jump in and hit the gas pedel it goes back to idleing normal. It never idles longer than 20-25 minutes before I jump in and go. Could this be a built in saftey for the pump? I never noticed this before I changed the transmission. Maybe PCM related? It doesn't seem to be causing any ill effects on the truck, just curious.

 

[ToolManTimTaylor]

Famous TSB 18-019-01

Cummins High Idle feature enabled?





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)

 

[BWillard]

Thanks Tim,



Wonder why it never happened with the automatic?

 

[ToolManTimTaylor]

Some have it , some do not , some bring it to have it do it , some don't , some do and don't , some don't and do do it get it

 

[Billy Diesel]

I have the high idle enabled, and it only takes a minute of idleing before it engages. Also, it stays at a constant 1200 rpm. Only my homebrew high-idle will fluctuate rpm's according to the grid heaters cycling.



If it is the high idle, it may be looking for the signal that the transmission is in park, but since you switched to the "correct" transmission, the signal is not there?



Just my WAG

 

[ToolManTimTaylor]

Originally posted by BWillard

Now I know that the VP44 isn't supposed to be idled for extended peroids for lubrication purposes, It never idles longer than 20-25 minutes before I jump in and go.

Also on another note,

Extended Idling is bad not for VP44 Librication. It's frowned upon because of a condition called cylinder washdown , and a varnish buildup on intake and exhaust valves. When idling a dead cold motor the cylinder temps really do not get over 230 degrees. Take into consideration the sheer mass of the cummins engine block and it simply just acts like a giant cooling fin. Cylinder washdown also can add a fair amount of diesel to your crank case , wash down valuable oil film on your cycinder walls (After all diesel is a form of kerosene which is one of THE best parts cleaners known) leaving just diesel as a lubricant.



That is why there are things like high idlers , exhaust brakes , espars and things of the such that you can use to work the motor at a small percentage of load to maintain heat.



A few links



Washdown



Varnish

 

[ntillm01]

It sounds like the Cold Idle Feature, but 20 minutes before it kicks in?!?!?!?



I know the bulletin doesn't say how long before the idle ramps up, but several have posted out there it only takes about a minute. I have also read from posts that it kicks back in when temps fall back down to that range.



Bwill-Is your heater pluged in, then you let it idle? Maybe it cools off enough after 20 minutes of idling that the cold idle option ramps up then?

 

[BWillard]

I leave it plugged in all night and while warming up. When I come out I unplug and go.

 

[ntillm01]

I'm thinking you still might be dipping into the range that the cold idle kicks in. Even with the heater plugged in, it can't keep up as well with the coolant circulating. Takes 20 minutes to cool everything else off to that level. I could be half-way to the moon with that idea though.



I don't like the surge part of it though. Is this a new thing that the truck's never done before? If not, I am curious as to what may have changed or what's acting up.

 

[Turbo Tim 1]

Did the ECM get reprogrammed for the standard transmission? If not I would think it's something to do with that. The cold idle thing should be a steady 1200 rpm after conditions are met unless maybe one of the sensors that make that work is messed up.

 

[ntillm01]

Turbo Tim-I missed that completely. Guess I should read the BOMB-section before I open my mouth.

 

[ToolManTimTaylor]

Actualy Tim good point. The PCM and ECM are two different animals in standard vs automatic trucks.

 

[BWillard]

Yeah, I never changed my PCM/ECM when I swapped out the auto. The only thing I lost in the swap is the cruise control (speed sensor is on the auto)so if it is the high idle feature and for some reason it's not reading the signal, why didn't I have it before?



ON THAT NOTE, where is the speed sensor for the standard transmission located? Maybe mixed in to the rearend harness and fed through the speedo somehow? I would like to get the cruise control back.