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P1120 tps out of range low

RavoHimself

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So 2 nights ago my truck started idling at like 1400 and hangs/jumps to like 2k-2500 between shifts. Got the code so I put in a new bwd tps. Still the same issue. So I replaced the IAC too and that didn't work either. I haven't checked the voltage on the tps yet but I know it's supposed to be within .6-1 at idle. Other than the I'm at a loss as to what to check next
 


RavoHimself

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I've since tried checking for vacuum leaks and cleaning the throttle body and MAF with contact cleaner and cleaned all the connections. The code went away after I or the new TPS in but it's still idling high. I'm really at a loss
 

RonD

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After engine is fully warmed up and idling, unplug the IAC Valve's 2 wire connector
Idle should drop to 500rpms or so, or engine may even stall, either is GOOD, it means no vacuum leaks

If idle stays high then there is a leak, assuming you haven't adjusted the Anti-diesel screw on the throttle linkage
With IAC Valve still unplugged you can pull vacuum hoses on the intake and cover the ports with your finger, if RPMs drop you found the system with the leak
Or spray soapy water around the intake, it should stall out the idling engine if its sucked in, and safer than spraying flammable liquids on a hot engine :)

If idle does drop with IAC Valve unplugged then the Computer is setting the high idle.
Could be ECT sensor is reporting cold engine all the time, although that should set a code.
Could be a glitch in the software, it occurs over time, you can give a Ford Dealer your VIN and tell them its a high idle issue, they can tell you if there is a software update available, this was not all that uncommon of Fords, or GMs for that matter.
You do have to pay for the time it takes to do the update but its the only fix if it's a software issue.
 

RavoHimself

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The idle drops right down to 400 or so with the IAC unplugged. I didn't think it was a temp sensor because like you said it's not throwing a code but also because it still does a full warm up circuit. It will start around 2k or just over and then as it warms up drops to 13 or so. So it seems like it's definitely getting a temperature signal. I'll have to call Ford I guess. Thanks for the suggestions
 

RonD

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Yes, see if there are any updates for the Computer
 

RavoHimself

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So I brought it to a local shop who I trust. I have the moddbox supercharger kit on there. Turns out there was a cracked hose between the bypass valve and intake. Don't know how I missed that when I sprayed down the entire engine bay but I'll be picking her up later. Thanks for all the suggestions
 

RavoHimself

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Well I'm unsure it's fixed all the way. The super irregular idle is gone but it still wants to hold the idle between shifts and it still doesn't always want to idle where it should. It's a lot better but still seems off. I'm gonna give it a couple days an see if it's the the computer trying to relearn
 

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