Throttle stuck at 50% - Help Please

[Mr_Carman007]

Hello all, thanks for allowing me into your forum!

Here goes my first post. I purchased a 2003 Humvee on Ironplanet in April and was thrilled to finally take delivery of it a couple of weeks ago. I purchased it with a note saying the “throttle sticks”. Well farting around with the truck it felt a little bound up, for example when I would push the pedal down to accelerate, the pedal had a point that it would go past and accelerate a little harder than i wanted it to.

I didn’t really worry about it too much until one day I let it warm up pretty good (wanted to make sure it wasn’t overheating because man this thing hits 220 degrees QUICK, like quicker than any other diesel i have ever had - never seems to have gone over 220 though which makes me happy). When I went to drive my daughter around the neighborhood, I got passed the “bound” part of the accelerator... but it never decelerated back down to idle.

I rode the brakes hard and limped the truck back to my house where I parked it. Whenever I start it back up it starts revving pretty hard (I shut it down before it gets over 1500ish rpm because i don’t know how high it really wants to go and I don’t want to cause damage).

Once I had a few minutes I opened the hood and removed the throttle cable from the IP and tried to restart... still revved.

Looked a little closer, and it appears as though the throttle is actually all the way closed (where the throttle cable meets the IP), but it is still revving.

So the short version of my question is, have any of you guys experienced something like this? I am really hoping it is not the injection pump that is the problem as my wife will be... well, less than trilled that I have to sink more money into a toy that she is not a huge fan of already lol.

Thanks in advance!

 

[frank8003]

Study how the throttle linkage works in the TM's, You'll figure it out.
TM 9-2320-280-20-1

 

[Steve1008]

I had a similar problem with my m1008 when I first got it started the engine and it wanted to run at high RPM only. had the pump rebuilt and it fix the problem. Your governor might be sticking.

 

[TOBASH]

On mine the problem was that sea air created corrosion that kept the spring from pulling the throttle/cable to the idle position. A stronger spring and some WD40 and more frequent driving fixed the issue. Ensure the throttle is at the idle position BEFORE you start rebuilding the unit. Work the throttle unit back and forth while the engine is off while spraying in lubricant. Ensure the Throttle unit has a full range of motion.

These vehicles sit for years before auction. Rust and corrosion happen.

 

[Andyrv6av8r]

It could be your automatic advance plunger being corroded and stuck. It sits on the bottom and water collects in the engine valley and rust and corrosion sit in. My 1045A2 was doing exactly as you describe. I sent my pump out for a rebuild and they replaced all bad components and overhauled it. Runs great now.

 

[juanprado]

I would also check temp with a heat gun or known good gauge. These trucks run cool and should not jump that fast. Might be a good idea to flush and fresh coolant if all is good.

Mine had a lot of crud and mud. Dont forget to flush heater also.

 

[Retiredwarhorses]

completely disconnect the throttle cable, manually rotate the throttle linkage, does it snap back on its own to full rest? Does It still race when fully at idle rest? If so...your pump needs rebuilding.
I’ve had pumps fail internally and run away...so this is not something you want to take lightly.

 

[diesel dave]

X2 what RWH said. I lost a Mack engine same way. Stuck on WOT and driver didn’t know how to shut off fuel.