High idle after IAC/TPS replacement (possible short?) - Jeep Cherokee Forum

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High idle after IAC/TPS replacement (possible short?)

Old 03-16-2019, 05:14 PM
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Default High idle after IAC/TPS replacement (possible short?)

Hiya everyone. I have a 1999 Jeep Cherokee Sport (4.0 of course) and no mods..yet. I recently replaced the TPS and IAC in her and when I started the engine and the rpm shot up to 3K, after turning it off I check the connector with a multimeter and a scanner tool (torque for android). The multimeter read that there was 5 volts at the consent supply wire and oddly enough 5 volts at the signal wire as well (plugged and unplugged). The scanner tool said when the wire was plugged into the TPS the throttle position was at 22% and unplugged it was at 99%. I'm assuming theres a short in the circuit? If so, where do I look now?
Thank you for your time.
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Old 03-16-2019, 05:30 PM
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Use the continuity setting of your multimeter on cords that you know are on the power side to a metal contact/ground.
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Old 03-16-2019, 05:36 PM
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Triple check you didn't knock a vacuum line loose somewhere. Air getting into the intake manifold is like opening the throttle plate.
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Old 03-16-2019, 06:51 PM
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I noticed that theres a jam nut screwed onto the setscrew that pushes against the throttle valve, I took it off (since it was shiny and obviously not an original part) and low and behold the RPMs wen't down to 825rpms. It did however started throwing codes: P0505, P0123, P123, p0122, and P0108. I'll check the youtubes and nets but what do you guys think?

Last edited by Jeepergirl; 03-16-2019 at 07:48 PM.
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Old 03-16-2019, 07:47 PM
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Update: I Took the jam nut off and cleared the codes by removing the negative battery cable connector for a few minutes and now she runs great! An even 727 rpm 's and no hard shifting.
My guess is that the previous owner used the jam nut to get it running right instead of properly replacing the TPS/IAC. Thank you guys, for the replies!
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Old 03-16-2019, 07:48 PM
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The codes are for IAC not working, TPS signal, and the P0108 is a high signal on the map sensor. I assume the TPS and maybe the IAC are from disconnecting the connector. The vac line for the MAP disconnected? Possible someone tried to fix a bad IAC with that extra nut? If the throttle wasn't sitting against the set screw, then it's possible the TPS is misaligned and not installed correctly - I had someone come to me with the same symptoms and they'd somehow managed to get the slots not lined up when installing it, which also made the throttle stick open too far.
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Old 03-16-2019, 09:59 PM
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U rock girl! If you are ever south of Brookings maybe I'll show you my TCM hack.
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Old 03-16-2019, 10:24 PM
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Originally Posted by DFlintstone View Post
U rock girl! If you are ever south of Brookings maybe I'll show you my TCM hack.
An I would certainly buy the first round.
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Old 03-16-2019, 10:30 PM
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Crescent City mountain hermit here. Really, you BUY your booz? It does ferment naturally ya-know.
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Old 03-16-2019, 10:33 PM
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LOL! Yes yes, life in Oregon made me soft. I rather not suffer from alcohol poisoning like that one time when I was 19 but if you promise that you know a reliable source then I'm always game. xD
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