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Old 04-09-2019, 09:54 AM   #1 (permalink)
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Help needed on fluctuating throttle

All right here's the situation, 91 3.0 285K miles, after initial start up and the engine has been running for 3 to 5 minutes, The idle fluctuates up-and-down. I think it may be a vacuum leak but I cannot find any. I have cleaned intake, added new Throttle Position Sensor. Can anyone point me into a different direction?
Thanks for your time
Mike

Last edited by welchdog; 04-09-2019 at 09:55 AM.
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Old 04-09-2019, 10:09 AM   #2 (permalink)
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Originally Posted by welchdog View Post
All right here's the situation, 91 3.0 285K miles, after initial start up and the engine has been running for 3 to 5 minutes, The idle fluctuates up-and-down. I think it may be a vacuum leak but I cannot find any. I have cleaned intake, added new Throttle Position Sensor. Can anyone point me into a different direction?
Thanks for your time
Mike
Low on coolant or bad cold start sensor.
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Old 04-09-2019, 10:18 AM   #3 (permalink)
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Coolant level good, I'll check sensor


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Old 04-09-2019, 10:33 AM   #4 (permalink)
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Is tps adjusted properly?
Are your IAC hoses clear?
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Old 04-09-2019, 10:39 AM   #5 (permalink)
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Is tps adjusted properly?
Are your IAC hoses clear?
Help me understand how the TPS could be adjusted. Will check the IAC hoses

Thanks!
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Old 04-09-2019, 08:25 PM   #6 (permalink)
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IAC hoses, and check for crack in the intake hose - if you're still running the factory set up. They're sometimes hard to see.
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Old 04-09-2019, 08:27 PM   #7 (permalink)
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IAC hoses, and check for crack in the intake hose - if you're still running the factory set up. They're sometimes hard to see.


Thanks Bob, it came with a KnN intake will check IAC hoses


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Old 04-09-2019, 09:03 PM   #8 (permalink)
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Where would I find the IAC, I'm very handy under the hood but WTH is it



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Old 04-09-2019, 09:23 PM   #9 (permalink)
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Have you checked for leaks with some sort of accelerant?
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Old 04-09-2019, 09:25 PM   #10 (permalink)
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Have you checked for leaks with some sort of accelerant?


No, I'll put that on the list too


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Old 04-17-2019, 07:53 AM   #11 (permalink)
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Update: there is NOT an IAC on these vehicles, so I cleaned the cold start valve and let the engine run for 5 minutes, idle was a little high, but from my research this is normal. Will update after I run the engine longer.
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Old 04-17-2019, 08:50 AM   #12 (permalink)
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Idk where you are getting your information. There is in fact an IAC. Its what the coolant hoses on the TB attach to.
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Old 04-17-2019, 01:33 PM   #13 (permalink)
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Idk where you are getting your information. There is in fact an IAC. Its what the coolant hoses on the TB attach to.
Since you are the only one to state that, and I am NOT doubting you, do you have a diagram or link to a diagram that shows it?
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Old 04-18-2019, 06:44 AM   #14 (permalink)
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Do yourself a favor and find an FSM

https://www.yotatech.com/forums/f116...-valve-292172/
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Old 04-20-2019, 03:20 PM   #15 (permalink)
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Update:
Found a link to a FSM, pulled the throttle body today, NO WHERE in the FSM does it mention an IAC (not one that can be purchased from a parts store and replaced), the coolant hoses running to the TB were not clogged. I adjusted the TPS (didnt think it was possible) per the FSM.
Bottom line: clean cold start valve, adjusted TPS, cleaned intake and TB, seems to have solved my issue.


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