ISL Engine Idle Adjust (Thanks Gordon66)

[Diplomat Don]

For the past year or so, my ISL 400 has been idling rough when I come to a stop. It would idle about 50-75 rpm to slow. When I would give it a few rpm's worth of throttle the idle would smooth out and the coach would be motionless at a stop.

For the longest time I've been trying to find out why my coach's idle was low and rough. I was at the point where I was going to do something that just boils my blood to do....take it to a shop for diagnosis.

The other night I was reading a post by jwinston "Found High Idle Feature" and I thought I would open the post and see what was being discussed. I know about the high idle feature so I didn't expect anything new. Then I read the post by "Gordon66" that discussed the ability to change the overall engine idle speed. I sent Gordon a PM and he confirmed that you can change the engine idle by pushing the "Resume" button to raise the idle and "Set" button to lower the idle (on a SmartWheel) while the engine is running, in neutral and the cruise control OFF. Once you adjust the idle to where you want it, turn the cruise control on and this sets your new idle speed.

I ran the procedure this evening and reset my idle and now my ISL idles as smooth as silk.

Gordon66 said this was shown to him by Cummins. I really want to thank Gordon66 for saving my sanity and making my coach idle smooth again.

I really thought this is something that should be shared. I now realize that I probably lowered the idle one day when I hit the "Set" button to turn the fast idle on when the cruise control was off. Once I turned the cruise on, it set my idle lower.

[EngineerMike]

Don- what was your idle speed when idling rough, and what is it now?

[bullydogs1]

Don

I didn't know that would stick...thanks for something I honestly didn't know..I use the high idle with it on then shut it off..never knew you could reset it by doing it with it off...then pushing on.

[RJay]

Don, good info. So how would you set the high idle without changing the normal idle speed?

[Diplomat Don]

EngineerMike....Since I can only go by the dash gauge (which I'm sure is less than accurate) I went from about 700 to 750.

bullydogs1....The procedure I gave above is just to set the engine idle for driving conditions.

RJay.....per the original post by jwinston, it looks like you can raise the High Idle up by 100 rpm by using the Resume and Set buttons. I don't know if you can make this permanent.

The BIG issue for me was that I think I inadvertently lowered my idle a year or so ago when I was starting the coach. It's easy to do. If you typically start the coach, wait for oil pressure and then push SET to start High Idle you could lower your engine idle if you didn't turn the cruise on, realized you didn't and then turned it on. By doing this, you just lowered your engine idle speed. Since the adjustment is in small increments, I'm thinking I may have done this a few times over the years.

I wish I would have asked how to raise the idle a long time ago. Fear of looking stupid prevented me from doing so....so I how stupid do I look now. Being such an anal retentive twit left me aggrevated everytime the coach idled rough at a stop. A years worth of aggrevation. Even my wife is happy she won't have to hear me grumble about it now.

Does it show that I'm happy about this discovery?

[EngineerMike]

Don- you shouldn't have any rough idle @ 700. I'm guessing that your tach is digital and fairly accurate. Mine (Actia brand) reads the J1939 bus data stream which includes engine revs, and a stepper motor moves the needle to the appropriate position to indicate revs. I can read the needle within 10rpm (the Actia speedometer has an LCD readout where I can switch from reading odometer to reading engine parameters, which include rpm, so I've checked the accuracy). I was guessing you were in the low 600's when I read your post, but that's what triggered the question.

I believe your engine was supplied by Cummins, Coburg, and I'm guessing they have someone who worked on Monaco supply that would answer a question about whether rough idle around 700 indicates a problem. Obviously there will be a lower limit where the fuel/air table won't function to keep the engine turning smoothly.

[Diplomat Don]

Mike.....Monaco uses old dial gauges. Most of the Monacos are way off. My oil pressure reads 30 at idle and 15 at speed. I know that's way off. The trans temp gauge only moves a couple degrees from the cold temp. The gauges just aren't acurate. The only thing I can say with some accuracy is that I bumped the idle about 50-75 rpm when I nade the adjustment. It was just enough to make it soooo smooth I could barely feel it running.

[brrving]

Yep.. Same here!

The idle on my 400 ISL seemed to be slower over the last year or so too and I couldn't understand why. I saw the same post and made note of the change procedure. The same thing had to have happened, inadvertently lowered it when using the fast idle.

This is why this forum is so great!!

[jwinston]

FYI,
Diplimat Don.
My trans temp was only reading slightly above lowest till I cleaned the connection on the TC located on the tranmission . On my 99 Windsor it is a single spade lug connection on the bottom of trans near the drive shaft. Removed cleaned and applied dielectiic grease and trans temp now reads more accuratly. Still a litttle low as most of the engine dash gauges are vs what the VMSpc software is reading that I use to monitor all engine paramerters with a lap top. it is my understanding that the accuracy of the dash gauges is less than the engine/ trans sensors them selves. Engine / trans manufactures use higher accuracy sensors to ensure protection in out of tolerance conditions.. James