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Here is the deal. The throttle sticks open on my engine DD 8V92 Silver 475 hp). Started out intermittently but now it does it consistently. I first thought it was the cable from the air cylinder to the throttle lever. In fact it was sticky so I replaced it. Next my beautiful assistant operated the throttle pedal while i observed the engine with it not running. The lever operated full on to full off every time. Then I started the engine. When the throttle pedal was depressed the engine went to full rpm and would not return to idle when the pedal was released. I went back to the engine and the cable had released the throttle lever but the lever had not returned to idle. I easily returned it to idle manually. Is perhaps there a spring missing that pulls the throttle back? I am perplexed. I hope it is not a failing governor or the like. I am considering installing a spring return for the throttle. Cant drive it this way. Too much of a thrill!

[Tf175]

Tim ,
I will attempt to attach a picture of my throttle linkage , taken with intake hoses off . There is a return spring .                

[Tf175]

I looked at pdf Detroit service manual , a spring is shown on the stop control shaft (inside governor housing ) , but I see no spring on the speed control shaft . Also looked at Powerline Components online parts catalog , and they show a "booster" spring and bracket . If memory serves , my spring is anchored on the shut off solenoid bracket . As shown in picture , I installed a new spring and cable ( rebuilt cable , California Push /Pull ) .
Owing to the importance of a properly functioning throttle , any opinions welcome .
Chris

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The pictures are priceless. My setup is basically like yours except no solenoid. Sounds like the booster spring might be the ticket. I can't seem to find that spring on Powerline site though. Do you know what part number it was?
Thanks so much for the help. Newell Gurus are the best!
I got my cable from CA PushPull also. Great folks.

[Tf175]

Actually,  I was looking at the parts catalog to make sure there is external spring . Not sure the set up shown in Powerline would work , but it's pg 128 in 8v92 cat , throttle control section .
Is there another lever near the speed control lever on the governor?  That is the fuel shut off lever , something will be there to activate it when you switch off . Mine has the air /electric solenoid that pushes against the lever to shut down. 
I will post another picture in the morning,  better Internet at the shop .
I sourced the new throttle return spring from McMaster Carr , tried to match old spring as near as possible .
One last thing,  Kyleb has a really neat throttle set up using a Williams air throttle . Look in Driveline/Williams air throttle,  vicinity of 2/2018. Couple of pictures there . I have all the parts /material to build that when time available.

[Tf175]

   
Picture taken when radiator was off . Look between fan blades @ one o'clock . Shut down solenoid with air hose , throttle lever , spring , etc .

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That is the way mine is constructed also now that I have crawled up in there. Should be able to add a spring pretty easily.
Another question you might be able to answer. Where is the coolant temp sensor located? Is that it between the fan blades at 3 o'clock in the picture? My temp gage on the dash is not working and i am trying to troubleshoot it. There is a loose wire that reaches that point on my engine.

[Tf175]

Yes , that is the water temp sensor,  just below thermostat housing for passenger side. It is very important that you have an operational temperature gauge . I recently added a second gauge with sensor installed in driver's side . The gauge is from Max tow .
The original gauges have a reputation for inaccuracy,  but I have to say mine reads very close to the new gauge . Advantages of the Max Tow is visibility and digital read out as well as analog .
Get a reliable engine temp gauge working on your coach , whether you fix original,  add another or both .
I sourced throttle return spring from McMaster Carr,  can probably get a P/N if needed .

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Sourced a spring and it works like a charm. Throttle returns as it should. Thanks for walking me through this!

Also, thank you for the advice on the temp gage. The throttle was #1 and then the cooling system. Going to pull the radiator and have it cleaned as the fins are pretty clogged up and i suspect the core is dirty also.
When I picked up this coach the only temp gage working was the oil temp. It created a lot of anxiety with only the oil temp gage working on the drive home.

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Air throttle pedal was squeaking so I disassembled and cleaned it up and lubricated it. For the life of me I can’t get the pedal spring installed. Anyone know what the magic is? Special tool? Can’t seem to find any help online, videos, etc.