We have a Tacoma that's a farm truck, 2012 I think. It sat a few weeks and rats made a nest under the hood, and chewed on some of the wire harnesses. I don't see any actual wires chewed through but the harnesses have multiple holes.

The truck starts fine, and then dies. If you press on the accelerator after starting it will keep running.c but as soon as you let off, it does immediately.

I ran that through ChatGPT and it said :

Quote:

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Most Likely Cause: The Idle Air Control (IAC) / Throttle Control Circuit is Dead

On a 2012 Tacoma (especially the 2.7 and 4.0), the engine cannot idle unless the ECM can control airflow through the throttle body.

If the rats chewed:
The throttle body connector,
The ETCS (Electronic Throttle Control System) wiring, or
The IAC / idle control circuit in the throttle body,

then the truck will:
Start normally
Rev/runs if YOU hold throttle open
Immediately die when you let off
Show NO warning lights at first

This EXACT pattern points away from fuel pump and definitely toward throttle body / idle control wiring damage.

When you push the accelerator, you're manually letting air in, bypassing the need for the IAC or ETCS idle control.

When you release, the throttle blade needs to:
Move to a precise idle position
Respond to idle commands from the ECM

If the ECM cannot see or control the throttle (broken wires), it can't hold idle engine dies.

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It also said it's a fairly cheap and easy fix.

But the question I have is what type of mechanic to take that to. Is that something pretty simple, or does it need to go to a dealer? What can y'all tell me to help get this resolved?

What city?

Near Stephenville

Do you have a trusted local shop?

The shop I use in College Station said they deal with this about once per month with people bringing in Toyotas. They know what to do.

If you have a shop you use regularly I wouldn't go to a Stealership.

do you have any codes?

Based on your description and the history you outlined, I'd start with looking for a vacuum leak cause by rat damage. Rats, when they make nests, will chew or gnaw on anything that is in their way. I had this happen to a wire harness and vacuum tree harness on my truck. I had to rebuild everything.

It could be IAC failure, but I'd start listening for hissing and see if it's not an even easier fix.

Check the air box for a massive nest that is choking the motor as well.

Your wiring harness, while not chewed completely through, could have expose wires that are shorting out and killing whatever signal shouldn't be killed. Make sure they are actually unsevered and go ahead and fix those to avoid shorting issues or corrosion. Wires that are exposed can corrode or short and that is what causes electrical gremlins that are an ass pain to chase.

Squirrels not rats.

Had it done on my 2021 f150. Insurance handed it, $4500.

I thought that price was Highway robbery, but the insurance adjuster told me that what happened to me is fairly common and that's actually what it cost to replace the wiring harness down in my engine.

First open the air box and make sure it's not packed with cotton or whatever blocking all the air. Next peel the visibly chewed loom back and see if you can find a cut wire. Should be pretty easy and if you don't want to do it any halfway decent mechanic should be able to diagnose and repair it

Thanks for the feedback.
No codes.

Found a nearby mechanic that a relative recommended that said they'd dealt with multiple of those problems in the last couple of months. I guess we will see what the damage is.

And then go on the warpath against rats and mice. At least for a little bit.

The mechanic said they'd chewed thru the harness in several places and they replaced the entire harness, that along with a new battery was about $700.

I see there is some tape you can apply to the wiring called rodent tape that has capsaicin in it to prevent chewing. To me it seems like that would only work if you covered every bit of the wiring.

There seems to be some mesh like covers you can put over the wiring to also prevent chewing. But like the tape, if you leave an inch exposed, does it really matter how much is covered?