M923A2 Idling RPM

[RedOctober]

This may be a stupid question but I have been doing maintenance on my M923A2 such as oil changes and trying to get the CTIS to work while I wait for title to come in. I noticed that my engine upon start up idles very high around 1000 RPM. My question is, is this normal is it something these trucks do to heat up the engine and transmission to operating temperature, or is this something I need to address and fix?

 

[Carlo]

Neither one of my 2 A2's do this or my M923A1 BUT my M931A1 did this and it was because it was sucking air from numerous places of fuel tubes from the tank to the first filter and even after the filter to the pump. The hoses look good but when you pressure test them I found more than 6 leaks.
How are your filters? Fuel condition?

 

[RedOctober]

Filters were changed by army 2 years ago. I am in the process of changing them myself now. And I filled the truck up with diesel when I picked it up and drove it home and the fuel didn't look bad then.

 

[Carlo]

It sounds like it's sucking air. Try pressurizing the tank and look for fuel leaking from hoses. I have heard from other members that even pickup tubes in the tank can have problems.

 

[RedOctober]

Ok, this maybe my limited mechanical knowledge speaking, but if it was sucking air wouldn't the engine cut out or sputter do to air getting in the system?

 

[Carlo]

I understand what your thinking but my 931 would rev up but it was a no power type rev. Does it ever die after it revs up? Does it start hard?
I would start with the easy stuff first as in filters and go from there.
Hope I helped.

 

[RedOctober]

I appreciate the help I'm just throwing thoughts out there. And to answer your questions no it has never died and it starts with a simple turn of the switch and I am not holding down the gas pedal or anything when I start it. I will replace the filters and stuff and provide an update. I am just trying to think of a way to pressure test the system now.

 

[Carlo]

To find my leaks I wrapped a rag With tape around the air hose then just a little presure at a time pumped air in. I then followed the tubes to the pump and found the fuel seepage. I also would disconect the fuel tube at different points to check flow.

 

[Scott88M]

This might not have anything to do with your problem but if you look under the hood on firewall where pedal comes through there's a spot where the hand throttle cable is connected. Sometimes mine gets stuck on the bracket and basically acts like hand throttle is partly pulled out.

 

[Carlo]

This might not have anything to do with your problem but if you look under the hood on firewall where pedal comes through there's a spot where the hand throttle cable is connected. Sometimes mine gets stuck on the bracket and basically acts like hand throttle is partly pulled out.

This could be right. My M923A1 would sometimes not return to idle. I checked at the pump and gas Pedal was not returning to the idle position. The spring was good so I checked the gas pedal in the cab and it was hangng up. I lubed the pin / pivot and it worked.

 

[RedOctober]

Thanks for all of the help guys. I checked the pedal today and sure enough that was it. the pedal was really stiff in my truck and it was not returning all the way to the neutral idle position. I am going to lube it up and see if that fixes it.

 

[Carlo]

I also hit the pin to give it a little more play plus the lube.
Im glad we could help. That's why we are all part if the club. 2 years ago I had the same problem and I had help from 50 people in 12 hours! I'm still in touch with many of them and will never forget their help they gave me.
Stay in touch!

 

[Scott88M]

I had to almost remove the hand throttle nut it was getting caught up every time I drove it