High idle, need help!

98 3.4 v6 5spd with a high idle at 1.5k to 2krpm (even after warmed up). I replaced the PCV valve problem continued. Took it to a local shop, they changed the air filter, cleaned the throttle body, and cleaned the mass air flow sensor, problem continued. At this point, they told me I could walk away as is with a $200CAD bill, or have them change the IAC valve and have a $1100 CAD bill (new part was $550), but that it will 90% fix the high idle problem. I told them to go ahead with replacing the IAC valve.

Just picked the truck up and they told me to wait a few days for the idle to re-learn or whatever, but truck is still idling high at 1500rpm. I'm doubtful that waiting a few days for the computer to re-learn will drop the idle back to normal, and kinda annoyed that I potentially just wasted a bunch of money. They said if problem continues to take it to a Toyota Dealership. (like wtf?, I told them I would be taking it back to them).

Wondering if anyone has any idea into what is causing the high idle, after already going through the likely causes (throttle body, maf sensor, iac valve, pcv valve?

Any help is appreciated. thanks.



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update 9/18/23

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



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9/27/23

Update, dealer says the throttle body butterfly flap is worn out, so to replace. But that they don't make OEM throttle bodies anymore, any leads on where I can find an aftermarket one, or shops that rebuild throttle bodies. They also said it could be the ECU (which they also don't make any more) , but that it's more likely to be the throttle body. Anyone have any experience getting it rebored from Maxbore? looks like I'll try that.

Found a throttle body local to me off a 98 4runner, same year. Will it matter if it's auto or manual, or will it be the same? (mine is manual for reference). Also does it matter if it has cruise control or not?

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9/30/23/

update on page 3


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10/20/23 Final update pg 3. Solved.

 

Vacuum leak, sticky throttle cable, faulty TPS

 

Ruled out throttle cable and vacuum leak. it's also not throwing any codes so I don't think it would be the TPS.

 

Do you have a scanner? Can you hook it up and reset the ECU?

 

Did you get your old IACV back? Wonder if they even change it.

$1100CAD and told to take it to Toyota if issue persist, WTF?

 

When you say you've ruled out the throttle cable- did you check to make sure it's also not too tight? Mine was ever so slightly too tight and caused the idle to sit @ 1k when warmed up. It's easy to over tighten them as you try to take the slack out.

 

Yes I have a cheap one, reset ecu and it didnt fix the idle?

I didnt get it back, but by looking at it it does look like they changed it. Yeah exactly, I was expecting for it to be fixed, and they didnt mention the toyota dealership thing until after I went to pick the truck up.

I essentially ruled the throttle cable out by checking that it wasn't too tight. There is still a bit of slack in it when I pull it by hand. Mind you this is all I did and it was pretty rudimentary, is there any other way I can check? The throttle also doesn't move backwards when I move it by hand, so it's not like its stuck in a high idle position if you get what I'm saying


For what it's worth, I went travelling a before the summer for a few months, and when I came back thew trucks battery had died so I replaced it. I recall this idle thing happening around the time I returned home and replaced the battery

 

there is a possibility that the throttle body bushing are wore. Grab the throttle bell crank and try to manually close it by hand while wiggling it in and out and up and down to see if it is actually worn. If your scanner is capable of live data tell us what the fuel trims are, both short and long term, if is in closed loop or open loop, what the intake air temp is and what it says the coolant temp is.

 

My scanner is super cheap, doesn't have that capability

 

Is it reporting a cold coolant temp? Is it in closed loop? Need a decent scanner to find out

 

No idea, I took it to a reputable shop so I would assume that they did that in their diagnoses process

 

take it to an oreillys and let them run their code scanner on it and see what it says, write down the information and see if there are any pending codes too... what ever you do dont buy the parts recommended.

 

You paid an extra $900 to replace the IAC valve, am I reading that right? There's no way that job costs that much and that part is may be $250 at a dealership.

 

This guy fixed his with a Throttle Position Sensor

https://www.tacomaworld.com/threads/3-4-high-idle-solved.522019/#post-16793192

Didn't read this one

https://www.tacomaworld.com/threads/fixed-high-idle.704758/

 

Essentially, yes. Paid the extra for them to clean and test the IAC, and then to replace it since cleaning it didnt work. My dad has been going to this shop for a few years and they are usually pretty good, but I probably won't be going back.

interesting, I'll look into the TPS

 

If your scanner can't do a reset just yank the battery cable for 1/2 a beer that should reset it. I'd recommend a nicer scanner (Amazon has a ton of bluetooth ones) that can pull live data. Failed coolant sensor can give you weird results too but I'd focus in on the TB sensor, did they plug everything back in?

 

unplugged the battery and reset it. Gonna drive it for a few days and see if the idle resets. will report back after that. They scanned it and said it wasn't throwing any codes, and everything looks to be plugged in.

 

Waited a few days for idle to re-learn and still hasn't gone down. Not sure what the problem could be??? Banging my head against the wall...

If it's not throwing any codes, is there any point in replacing the throttle position sensor? Would rather not replace things that don't need to be. Gonna take it back to the shop and make sure it wasn't/isnt throwing any codes

 

I replaced my TPS last year, there's an adjustment you can make with it before you tighten down the two screws. I had a bit of a goldilocks situations where my first attempt had too low of an idle, then too high, and I finally got it right the third time. It wasn't throwing any codes during these adjustments, FWIW. You might try fiddling with the positioning of your TPS.

 

Alright bit of an update. So I plugged my code reader in, and it's throwing a p0136 (o2 sensor) & p0505 (idle control system malfunction). The shop never told me about these codes, but was able to see them with my cheapo scanner. Any idea on what this means and what I should do now? There's no check engine light on btw.

The o2 sensor behind my cat was rattling several months ago so I used stainless steel zip ties to keep it snug and it seams to have held fine since, but could this be related to that? Obviously I'm inclined to believe that the high idle is to do more so with the p050 code and less with the p0136 code.

any help is appreciated, cheers