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Old 01-16-2023, 03:35 PM   #1
Mini-Skoolie
 
Join Date: Apr 2022
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2003 t444e idle acceleration

Our 2003 t444e/allison 2000 when idling will start to accelerate after some time. Just a quick press of the throttle will stop it. Seems to happen after idling every few minutes. Any ideas of causes or fixes. It doesnt seem to go to an unsafe level but it concerning especially if I leave the wife and or kids while I run in to get my change etc.

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Old 01-16-2023, 07:24 PM   #2
Bus Crazy
 
Join Date: Oct 2020
Location: Near Flagstaff AZ
Posts: 1,606
Year: 1974
Coachwork: Crown
Chassis: "Atomic"
Engine: DD 8V71
Do you have an air throttle system? If so, the treadle valve might be leaking which would create the symptoms you're seeing.
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Old 01-17-2023, 07:45 AM   #3
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Join Date: May 2009
Location: Columbus Ohio
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Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
if the weather is chilly this is called CAP.. and its turned on standard on all T444E's..
it is called Cold Ambient Protection.. after 5 minutes at low idle the bus will idle itself up to a maximum of 1450 RPM.. and attempt to reach a coolant temp of 170.. when it starts to get close the idle speed will automatically come back down.. I think this activates anytime the intake air temp sensor reads 45-50f or below.. id have to read the manual on it again to be 100% sure...



all you have to do is touch the accelerator or brake pedal in less than 5 minuite intervals and it will reset that timer


you can typically tell when the system is armed.. as when the bus starts up in semi-cold mode it will udle up to 900 RPM until coolant temperatures reach osmeplace around 85-90 then it comes back to the normal 700 (unless CAP activates)...


in REALLY COLD weather, the engine will idle at 450 RPM until the Lube oil PSI reaches 20-30 PSI then it will slowly come up to 900.. (and higher if CAP activates)...


im not sure if these features exist on the DT466E or not.. you can turn them off in the ECM if you dont like them..
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Old 01-17-2023, 07:47 AM   #4
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Join Date: May 2009
Location: Columbus Ohio
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Year: 1991
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Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
I should add that if you park a Warm already-driven bus and idle it.. the coolant temp will drop from heat being removed by the heaters.. and CAP will acticvate as the coolant temp drops further from 170... its not just a startup thing..
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Old 01-17-2023, 12:37 PM   #5
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Damn, Christopher, that makes sense. And it's clear that I don't know much about these newfangled computerized engines. I think of things in terms of mechanical causes and didn't know about this.

So, Sparky, forget what I said. And thanks, Christopher.
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Old 01-17-2023, 02:11 PM   #6
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Quote:
Originally Posted by rossvtaylor View Post
Damn, Christopher, that makes sense. And it's clear that I don't know much about these newfangled computerized engines. I think of things in terms of mechanical causes and didn't know about this.

So, Sparky, forget what I said. And thanks, Christopher.

the only reason I know is because the first time mine started speeding up I of course (coming from working on old mechanical diesels) thought it was getting ready to run away and blow up!!!


till I ran into the cab pulling the hood latches on the way.. and turned the key off (just to stop any fuel).. and to my surpise the engine just shut off like normal....



so I got the books out and started reading... and found the option in my computer where it exists and it was (is) turned on..
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Old 01-21-2023, 09:49 PM   #7
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Sorry it took me so long to get back to you all. I want to say it did it in summer as well (in phoenix). I know its not a mechanical throttle. Ill have to look at it closer in the morning. I assumed it was electronic but I'll check for air lines I'm guessing?
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Old 01-22-2023, 04:34 AM   #8
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Join Date: May 2009
Location: Columbus Ohio
Posts: 17,532
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
Quote:
Originally Posted by Desertsparky View Post
Sorry it took me so long to get back to you all. I want to say it did it in summer as well (in phoenix). I know its not a mechanical throttle. Ill have to look at it closer in the morning. I assumed it was electronic but I'll check for air lines I'm guessing?

if its truly a pedal problem or issue with the TPS and not the CAP system then tapping the brake pedal would have no effect.. the CAP is disabled by tagging the brake pedal .. since the engine will allow you to press the go pedal and the stop pedal at the same time you would still have Revs if this is an issue with the sensors in the pedal..



you might also want to read the computer and either turn the feature off and see if that changes anything or make sure the coolant and oil temp sensors are reading erroneous values.. if say in summer the coolant temp sensor things its 35 or 40 degrees when its really 60 then the system would likely arm.. im trsavelling (by plane) so I cant look and see if there is a setting temperature to trigger the system.. ive never known mine to activate in summer.. but maybe since in summer i usually load the engine down by starting the bus and turning on the A/C it warms up fast enough not to come on..
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Old 01-23-2023, 12:01 AM   #9
Mini-Skoolie
 
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It looks like it's electronic to my untrained eye and not an air system. Ill have to try some of those things when I get a chance. I appreciate your help.
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Old 01-23-2023, 03:20 PM   #10
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Location: Columbus Ohio
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Year: 1991
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Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
the T444E uses electronic throttle it is not an air throttle system.
the engine is drive by wire
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Old 01-23-2023, 04:45 PM   #11
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Location: West Ohio
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Year: 1984
Coachwork: Bluebird
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Engine: 6.9 International
Rated Cap: 65
I'm with Christopher assuming it's cap functioning. I wouldn't worry about it.

It's only supposed to come on below 40F. The fact that it comes on above that says that you might have a bad temp sensor which is causing it to come on when it's not supposed to. New trucks use an actual sensor to measure ambient temp, however something this old might fabricate that number from the manifold temp sensor, so use a scanner and see what those temps are. If the bus is cold and those 2 sensors don't read outside air temp then you found your issue.

I honestly wouldn't worry about it. CAP turns off when hitting the brake, gas, shifting out of neutral, or if the engine reaches a normal operating temp. It doesn't pose any danger to your kids/wife.
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Old 01-23-2023, 08:32 PM   #12
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Yep it's automatic to help the engine build and maintain a safe operating temperature in colder weather. My first bus that did that startled me too, but it's completely safe.

You're probably better off leaving it be than disabling it or canceling it by hitting the brake or throttle switch.
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Old 01-24-2023, 12:47 AM   #13
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Yeah. So my wife just told me it didn't happen is summer. So yeah as usual my memory was wrong haha. Ill try those couple things to totally verify I just wanted to get ahead of it. I appreciate all the help.
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Old 01-24-2023, 08:09 AM   #14
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Originally Posted by Desertsparky View Post
I appreciate all the help.
And I learned something new, from my non-help. Thanks, all!
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