Fast idle control affecting trans shifting

[Vanwill]

2000 Dynasty 36. Cummins 350 HP ISC Unlighted Smart Wheel.

I am having a problem with the engine occasionally raising its idle speed from a normal of 600 RPM to 750 RPM or higher. There is no mention in my owner's manual about raising idle speed using the steering wheel-mounted Cruise Control, but it has that capability, even though I've never used it. I have a dedicated rocker switch on the small console to the driver's left side, which raises the idle RPM in approximately 50 RPM increments.

I have owned the coach for four years and this just began recently. It seems the ONLY way to get the idle back to normal is to switch off the engine and re-start.

The problem this fast idle is causing is transmission shifting. Any time this fast-idle is enabled, the trans acts as if Economy Mode is canceled and it downshifts and upshifts at odd times. I suspect that when the trans computer expects to see a ZERO Throttle Position Sensor reading, and does not, it acts differently. Once the engine is stopped and re-started, the idle returns to normal and shift behavior is normal. Clicking the CC "OFF" button does not set the idle back to normal.

I'm not sure the fast idle is due to the steering wheel CC/fast-idle function, but I think that is the problem.

Can someone describe the operation of this cruise control fast idle feature when it is working as designed? How is speed raised? How is the function canceled? If you have a page from a manual that you can post, that would be great.

Anyone else ever have a similar problem?

Thanks!

[Flyin4Fun]

My 04 with Cummins 400hp does not have a steering wheel idle control... Or at least it's not being used, not labeled on any buttons! The idle button on the left console changes RPM in increments of 20... from 600 to 800. (5 clicks = 100 RPM) Sorry, I can't help. That's about the extent of my specific knowledge... any additional information would just be guessing.

[Steve Ownby]

Originally Posted by Vanwill

2000 Dynasty 36. Cummins 350 HP ISC Unlighted Smart Wheel.



I am having a problem with the engine occasionally raising its idle speed from a normal of 600 RPM to 750 RPM or higher. There is no mention in my owner's manual about raising idle speed using the steering wheel-mounted Cruise Control, but it has that capability, even though I've never used it. I have a dedicated rocker switch on the small console to the driver's left side, which raises the idle RPM in approximately 50 RPM increments.



I have owned the coach for four years and this just began recently. It seems the ONLY way to get the idle back to normal is to switch off the engine and re-start.



The problem this fast idle is causing is transmission shifting. Any time this fast-idle is enabled, the trans acts as if Economy Mode is canceled and it downshifts and upshifts at odd times. I suspect that when the trans computer expects to see a ZERO Throttle Position Sensor reading, and does not, it acts differently. Once the engine is stopped and re-started, the idle returns to normal and shift behavior is normal. Clicking the CC "OFF" button does not set the idle back to normal.



I'm not sure the fast idle is due to the steering wheel CC/fast-idle function, but I think that is the problem.



Can someone describe the operation of this cruise control fast idle feature when it is working as designed? How is speed raised? How is the function canceled? If you have a page from a manual that you can post, that would be great.



Anyone else ever have a similar problem?



Thanks!

Hey Van,

Hope you had a good trip to see the eclipse.

The idle speed smart wheel function is as follows:

1. Engine running in neutral with brake set.
2. CC must be off.
3. Press "resume" once. Rpm should raise 25-30 rpm.
4. Keep pressing until you are at 700.
5. Same drill with the "set" button will lower rpm.
Rpm should save & this will be new idle rpm until you change again.

If you do the same with the CC turned on you will engage fast idle & go up to 100-1200 rpm but it won't be stored.

[Vanwill]

Thanks for the reply, Steve.

Eclipse viewing was a bust--totally clouded over. But the trip with friends to Mountain Falls RV Resort near Brevard, NC was great.

[Steve Ownby]

Too bad about the clouds. We were lass than 50 miles from you in Sylvia & it was clear until after totality. Clouds moved in about 10 minutes later.

[oldguy70]

On my 98 there are 2 throttle return springs, if yours is the same make sure they are both there

[nehog]

Originally Posted by Steve Ownby

Too bad about the clouds. We were lass than 50 miles from you in Sylvia & it was clear until after totality. Clouds moved in about 10 minutes later.

We had a few very light scattered upper atmosphere clouds which actually made the eclipse pretty interesting.

Originally Posted by oldguy70

On my 98 there are 2 throttle return springs, if yours is the same make sure they are both there

I'm suspecting that on his there are no throttle springs and it has an electronic throttle.