Could someone give us advice on RPM's at idle on a Cummins ISX?

KW is idling at 500 RPMs and is extremely rough.

Is this normal? I thought it was at 600 and it seems to have changed by itself?...is this possible?...why?

Also.... how could we do an low idle adjustment? ...

Thanks! ...HELP...it is driving my husband crazy...I am not sure it is really that big of a problem....but we just bought this truck and he is freaking out over the rough idle ...

k

 

100 RPM drop sounds like an injector not working.

 

Actually, even with a problem such as that which causes a misfire on 1 cylinder, the ECM will still keep the engine idle at it's set speed, although the engine will run rough.

I know there is a procedure on a Mack whereby you can reset the engine idle speed within a range from 500 to 750 RPM, in order to get a smoother idle.
It is:
Vehicle stationary with parking brake on.
Accelerator NOT pressed.
Turn speed control on/off switch on and off 3 times within 2 seconds.
Depress and hold accelerator to desired idle speed.
Depress and release the set switch
Release accelerator.
Depress and release clutch pedal.

The new speed is now locked in the ECM as the new idle speed.

Check the Cummins owners manual, there is probably a way to do this on your engine too.

 

Is there a way to check codes?

I'm stabbing in the dark here, but I think he needs to check the crank sensor.

 

If there was a problem with the crank sensor wouldn't the engine be running poorly throughout the RPM range???

I agree that it should be checked for codes.

 

No, my dads detroit did that exact thing.

Changed the sensor, it was fine.

 

Doesnt crank sensor tell when to fire?...how would that relate?...

We might try resetting first....ummm...we will get back to you... thanks SO much... we will talk about it...

k

 

It might "scatter" at idle, and be fine at higher revs. Maybe it's loose, I don't know.

Have you called cummins yet?

Have you pulled any codes?

 

Appreciate all the feedback...just thought it might be a simple quick fix..

what may be loose?

thanks,k

 

crank sensor. I have no idea where it would be on your truck.