High idle, need help!

@Dm93 will probably chime in but I think it needs to go into closed loop for the idle to settle down. An oxygen sensor fault might prevent it from going closed loop.

Does the check engine light come on during bulb check? Maybe the bulb in the cluster burned out

I'm kinda questioning the integrity of a shop that would tackle a drivability issue and not even mention an O2 sensor code. But maybe it didn't show up until after they looked at it

 

Whats a closed loop? Yes engine light goes on when you turn the key halfway, but then turns off so it's not a bulb issue. Also just to clarify, my scanner was showing an orange light, not a red (it has three options, green, orange red), so I'm not sure if that means its a definitive for the p0136 & p0505 codes, or just a warning for those codes.

Same, I'll have to bring that up to them.

 

Closed loop means the computer is looking at the oxygen sensors for (feedback) fuel calculation

 

How do I get it into closed loop?

 

I'd start by fixing the O2 sensor fault

 

Let's take a step back- Your ECU will store pending codes. Faults that it has come across and noted, but haven't re-occurred enough to throw a light. So that's why you can read them with the reader, but the light is not on.

The fact that you did not fix the rear sensor properly is for sure a reason why you might get a code for it. Those sensors are measuring stuff in the exhaust stream, and you're potentially allowing that exhaust to escape throwing off the readings. Get that fixed reset the ECU and try again.

Open and Closed loop are automatically controlled by the ECU. When all the sensors are working, the ecu will "listen" to them and tune things, otherwise it uses a preprogrammed setup and ignores the sensors. You can't force it one or the other.. well, you could knock out a sensor and force that.. but that's not what you want.

 

i mean the bolts were rusted so i did this, i still think the sensor is fine? and this was a while ago where as the idle issue is recent

 

The P0505 essentially means the PCM is unable to control the idle speed, it could be a vacuum leak, bad or stuck IAC, open or short in the wiring from the IAC to the PCM, or a bad PCM.
You can test the IAC by applying power to it.

Actually on Toyota's the coolant temp has to reach about 174F before idle learn will begin, doesn't seem to matter whether or not they are in closed loop.
I think the OP has something else going on though since it's actually setting an idle code, there's alot of things that can cause it and the troubleshooting chart for that code isn't all that helpful.

 

Alright little update. Took it back to the shop and they told me nothing they could do, and to take it to a Toyota dealer. They said if it turns out to be an easy fix, or that the IAC they replaced is defective, they will refund me partially. I have no idea what the issue could be at this point so I guess I'm taking it to the dealer. Here's what they said they did, clean throttle body, asked tech about the butterfly flap and he said it was fine, checked for vacuum leaks, cleaned MAF sensor, cleaned IAC, and the replaced IAC with a new non-oem one. I asked tech if it could be the TPS and he said no. When I plug my scanner in I'm getting an orange (not red) light for the p0505 code. truck is steady idling at 1.5krpm

 

That's probably the first thing toyota is going to change

 

should I just order one and replace it myself then?

 

Did you fix the exhaust yet?

 

Exhaust is fine. Cleared the scanner, drove it 6 hours and it's not showing a code for the o2 sensor. I'm not in a position right now to weld on new studs anyways.

 

Good news for you- those studs are just screwed in there. Just need to twist 'em out, and put some new ones in there.

 

Are the bore or throttle plate wore out?
*image for example only

 

Not sure I understand, the threads are literally rusted, and new nuts won't screw on to it.

 

asked the tech and he said no

 

Ahh, the 'butterfly flap'.
I see now.

 

My 98 had the high idle after cleaning, checking everything else out. I purchased a low mileage throttle body and that fixed it. I took my throttle body off and held a flashlight behind it and I could see quite a bit of daylight and it had side to side movement so it was pretty worn out. I know you said the mechanic ruled that out but if you are not looking at it that way you can not tell by just eye balling it on the engine. Has to come off. It could be that or it could not.

 

Those threaded posts that you're saying are too rusted to thread a new bolt onto- those are threaded into the bung. Not saying these are the right size, but should get the point across: