Fast idle struck on

vegas39

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Hi all. So yesterday I was driving my truck, totally warmed up and my fast idle and timing advance turned back on. I always had heard that the sensor for these usually just quits working but mine seems to have the opposite attitude. Can I get a little insight on how to test that switch and what it's actually called? I ve heard talk in the past that they're hard to find when trying to buy one. Thanks!
 

miles1400

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go out to your truck when its cold and press down the throttle pedal. it should click in and sit a little bit lower than did before you pressed it. start the truck and it should be on fast idle. turn the truck off and the peddle should raise back up a bit. that means that the fast idle solinoid is working correctly if it doesnt do that its most likely a wireing problem.

i would also recommend you inspect you IP. it might be the throttle arm is getting stuck at fast idle
 

vegas39

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The fast idle solenoid and timing advance wire is energized when the truck is hot. I just need to know what and where to check.
 

vegas39

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Ok, so I just opened the hood and discovered I have a slight coolant leak where the upper hose is connected to the stat housing. Is that the sending unit for the fast idle and timing advance that sits below that? If so, it’s got antifreeze pooled around it. So now I guess can someone tell me what that sending unit is called and where to get one? I imagine it’s probably screwed up now.
 

Randy Bush

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This should help you, also the sensor or switch is right behind the upper radiator housing.
You must be registered for see images attach
 

vegas39

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Ok. Thank you for the info! I'm sure you guys are right, something is just coolant logged. I'll check back if I need more help.
 

IDIBRONCO

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From what I've seen, these don't seem to go bad very often. I probably have 2 or 3 more used ones sitting in my tool box, but I haven't had to use any of them yet.
 

vegas39

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Sorry for the late reply. Thank you for the part numbers. I finally had a chance to fix the leak and the switch is still acting up, so I'll be ordering one.
 

IDIBRONCO

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Here's a couple more question that I didn't see mentioned. Have you unplugged the wire on the solenoid? What does it do? Have you tried to unplug the switch below the thermostat housing to see what happens? Do both of those while the engine's running.
 

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