2006 Toyota Sequoia idle and rev problem

Reeve Kook

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Apr 2, 2020
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I had sprung a coolant leak that came from the heater core pipe, which involved taking the intake manifold off. I just got it all back together tried starting it, and it sputters out the first start or two. After that, it finally starts and stays running, and the RPMs go up and down repeatedly without touching the gas pedal. Also, pressing on the gas pedal does nothing, just keeps on doing the aforementioned rpm dance. I have a feeling this has something to do with this wire that I couldn't find anywhere it could plug into, I'm hoping that is the culprit. I have no idea what it goes to, or even how to search for it online. any help on explaining where this wire goes will be appreciated, thanks. I have attached a photo of the wire and connector in question.IMG-0189.jpg
 

Reeve Kook

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Apr 2, 2020
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It is also probably worth mentioning that a check engine light has come up, along with numerous traction lights.
 

Jgrauman

Active Member
Feb 18, 2019
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You're not going to like where that is plugged in... I can't even get a Pic of it. It plugs in straight down from where the clip attaches to the valve cover. Here's mine attached to the valve cover.
 

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Reeve Kook

New Member
Apr 2, 2020
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Oh it just occurred to me. It’s that little PCV valve under the intake manifold. So I have to take the top of the engine off again, yay. Could this cause the issues I am having with revving and idle?
 

Jgrauman

Active Member
Feb 18, 2019
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Oh it just occurred to me. It’s that little PCV valve under the intake manifold. So I have to take the top of the engine off again, yay. Could this cause the issues I am having with revving and idle?
I would assume so, yes
 

hugegrand

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Aug 12, 2019
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related to that... I have a separate yet related issue... One or both of The "Air fuel ratio sensors" (basically another bank of O2 sensors inside the engine) have gone bad and since the engine is very much electronically controlled, it's creating a cascading array of system errors. The only way to fix it is to remove the top end of the engine and do some other misc part replacements at the same time (suggested service). I've never had a TOYOTA this unreliable. I'm not sure if I'm gonna do it or scrap / sell it. I love the overall Truck, but a 4Runner / Land Cruiser it is not.
 

Jgrauman

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Feb 18, 2019
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It's the same engine as the other 2 models you mentioned. The A/F sensors are o2 sensors. You have 4, 2 on each side of the exhaust, one before the cat and one after. Is your exhaust in rough shape? O2 sensors don't last forever, will need to be replaced. If you have a scanner you can verify which sensor is working and which isn't
 

hugegrand

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Aug 12, 2019
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Thank you. I hear that. I am aware of them, and looking online I can't find much more info on what my mechanic was mentioning. He seems trustworthy tho... What he was referring to two sensors that are not part of the bank of 4 that are accessible under the vehicle but need to be accessed after removing the top end of the engine. I'm not saying you're incorrect either, I'm just working on how to address this. I may have misunderstood him, but he basically said he'd have to remove the top of the engine to access these two 'preliminary' A/F sensors.
 

Jgrauman

Active Member
Feb 18, 2019
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Thank you. I hear that. I am aware of them, and looking online I can't find much more info on what my mechanic was mentioning. He seems trustworthy tho... What he was referring to two sensors that are not part of the bank of 4 that are accessible under the vehicle but need to be accessed after removing the top end of the engine. I'm not saying you're incorrect either, I'm just working on how to address this. I may have misunderstood him, but he basically said he'd have to remove the top of the engine to access these two 'preliminary' A/F sensors.
I'm not sure what he is talking about
 

hugegrand

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Aug 12, 2019
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Major update!!!!

...and some restored faith in this slightly cryptic Toyota:

I found a great mechanic who was telling me the opposite of what all the other trusted mechanics around my way, and similar comments above noted etc.

I'm sure there can be mechanical causes, sensor failures, vacuum leaks etc, but he suspected an electronic short 'confusing the computer' and triggering a cascade of errors down the line.

He used a lap top to do some crazy electronic coms via the obd port and wayyyyyy above my pay grade. After making my truck do all kinds of werid clicks and whirrs and bla bla, he discoverd it was a harness connecting the two front O2 sensors. That was it. A simple short.

For me this also explains how the issue was random at first, then intermittent and had seemed to mysteriously self correct for about 4000 miles I'm guessing till the short went full FUBAR. The short was related to a wiring harness that connects the O2 sensors right behind the front manifolds. I figure it was slight wear at first, then it finally gave way on a strong bump or something when all the lights popped on again.

Happy ending! (So far) and thanks, I'm learning as I go.