Odd Idle Issue
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Odd Idle Issue
Im working on a '92 F250 351w 4x4 5-speed manual.
I primarily use it around the farm at lower speeds for random farm chores every day and the idle started kicking up whenever I pressed the gas to go and would stick there (not sure at what RPM) untill I pressed the clutch then it would drop back to idle but would still jump up and down. So found out my computer bit the dust and replaced it. That improved the idle but it still jumped around, so replaced the IAC and that stopped the up and down idle. I replaced the TPS a couple years ago before the computer fried. Now it idles smooth but when the throttle is pressed or goosed it holds the idle slightly higher for a couple seconds then drops, or holds idle higher while the truck is rolling (clutch in or out) untill I come to a stop then idle comes down. Any ideas what could be the cause of this? I've done a ton of research online and all I have to show for it is a long list of sensors to throw at it. Any help would be appreciated if this problem sparks any ideas. If yall have any question, ask away!
I primarily use it around the farm at lower speeds for random farm chores every day and the idle started kicking up whenever I pressed the gas to go and would stick there (not sure at what RPM) untill I pressed the clutch then it would drop back to idle but would still jump up and down. So found out my computer bit the dust and replaced it. That improved the idle but it still jumped around, so replaced the IAC and that stopped the up and down idle. I replaced the TPS a couple years ago before the computer fried. Now it idles smooth but when the throttle is pressed or goosed it holds the idle slightly higher for a couple seconds then drops, or holds idle higher while the truck is rolling (clutch in or out) untill I come to a stop then idle comes down. Any ideas what could be the cause of this? I've done a ton of research online and all I have to show for it is a long list of sensors to throw at it. Any help would be appreciated if this problem sparks any ideas. If yall have any question, ask away!
Hotshot
Joined: Jun 2015
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After retrieving codes, I’d check the throttle body for binding and carbon buildup. I have had several throttle bodies wear out over time. The shaft will move in the bushings allowing the butterflies to bind up. Just like the throttle shaft in a carburetor wears out.
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Since you never mentioned diagnostic codes I assume you haven't run them. Try this with a paperclip or a jumper like he uses. The code/s should help isolate the problem. Sandy
https://www.youtube.com/watch?v=p04NPv_gXsI&t=19s
https://www.youtube.com/watch?v=p04NPv_gXsI&t=19s
After retrieving codes, I’d check the throttle body for binding and carbon buildup. I have had several throttle bodies wear out over time. The shaft will move in the bushings allowing the butterflies to bind up. Just like the throttle shaft in a carburetor wears out.
Last edited by BrianJoyner93; Jul 21, 2019 at 06:07 PM. Reason: Afterthought, Add more info.
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Joined: Oct 2016
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From: Houston/Sugar Land
Great, I'll try retrieving codes but the check engine light hasn't been on. I tested the TPS and I'm not sure if the increase and decrease in volts is smooth enough to be considered good for what it's sending to the ECM but I've decided to go ahead and throw another TPS on it to be safe, so while I have the throttle body off ill clean it out and check it as well. I'm assuming there will be obvious play in the shaft if it's shot?
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New User
Joined: Dec 2018
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After retrieving codes, I’d check the throttle body for binding and carbon buildup. I have had several throttle bodies wear out over time. The shaft will move in the bushings allowing the butterflies to bind up. Just like the throttle shaft in a carburetor wears out.
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Fordman_Evs
1987 - 1996 F150 & Larger F-Series Trucks
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