Annoyingly High Idle

Hi All,

Been trying to solve my high idle methodically... i.e. not just throw parts at it.

Vehicle Info: '99 Tacoma, V6, 4WD, Manual, 221k miles

Issue: Idles at 1500 to 2000 RPM Cold and / or Hot

Had it in the shop for an alignment and the mechanic diagnosed it as a bad idle control valve (ICV). This was post a throttle body and and ICV cleaning by me.

I subsequently replaced the ICV with one from eBay that came in a Toyota box but no part numbers on it ($60). Problem seemed to get a bit worse after replacing it... Unplugging the ICV results in normal idle... albeit a little low but then throws off check engine light.

I don't have any intake leaks... been over everything multiple times.

Truck runs fine when driving... slow speed in 2nd gear can drive at 1k rpm no problem. Just when in neutral, idling RPM goes straight to 2k.

One other observation is when I stop from a higher speed, the RPM will bounce between normal (900 to 2000 RPM) like it's trying to idle normally but something won't let it.

Thinking I have either a 1) worn throttle body with a leak or won't close fully or 2) Bad throttle position sensor...

Attached a couple of screen captures from my ODB app of the truck at idle.

Any other thoughts?

 

I also tried resetting the computer (ie, disconnected the battery for 30 minutes)

 

As the throttle body ages it will develop wear in the bore and on the butterfly and will create a gap where they seal against one another. This gap will be filled with the carbon deposits that build up with the engine running. When a deep clean is done and all the carbon is removed then the gap allows more air to come around the outer perimeter and will create am annoyingly high idle.

My recommendation is to remove the throttle body and shine a flashlight from the backside. If you see light seeping around the perimeter of the butterfly then there is your issue.

you HAVE to remove the throttle body to really see if you have an issue, you will not be able to accurately tell with it still installed on the engine.

There is a company that does amazing work called maxbore.com I think its 150 for him to ultrasonic clean the throttle body and bore it out larger and create a new butterfly valve.


He is an example

 

Mine was cured by replacing the vac line that goes from the pvc valve to the intake.
I had replaced the pvc valve and that line with a silicone line. Going to a new stock line cured my high idle and lean issues.

 

Is this the $260 part you got for $60??
https://parts.camelbacktoyota.com/o...0YWNvbWEmeT0xOTk5JnQ9c3I1JmU9My00bC12Ni1nYXM=

You likely got a crap counterfeit ICV. That's why it's risky buying parts from Ebay or Amazon. If the price is too good to be true, it probably is. Especially since the problem got worse after replacing it. At least put the old one back in.

Engine parts are one of those places where I'd opt for OEM.

Also check the PCV system.

You might take it to a different mechanic to see what they say. If they say it's the ICV as well, have them replace it. That way you aren't the one throwing parts at it. If a shop does it, and that doesn't fix the problem, you shouldn't pay for all the parts they throw at it, only pay for what actually fixes the issue.

 

Here's the test procedure to the IAC / ICV. I was getting a super high idle when I swapped in a new long block, but my dumbass forgot to hook up the upstream O2 sensor and it wasn't going into closed loop. Test your old and new IAC.

https://www.tacomaworld.com/threads...upercharger-install-diagnosis-3-4-5vz.616967/

 

Check that your throttle cable is not too tight

 

Thanks! Yeah, I had seen reference to maxbore.com in my research for this issue. I'll definitely check out the butterfly valve more closely when I take it off again and use his services if needed.

 

Replaced both the PCV valve and line a few months back so these are good. Thanks for the suggestion.

 

Yeah, it was definitely a strange listing and I knew that I was rolling the dice on what would actually show up... plenty of good reviews on the part from the seller so took the gamble. Yes, probably after-market junk...

Here is the listing: EBAY Listing

Might try swapping my original back in...

Mechanic wanted $650 to swap it out... lol. If I have to buy true OEM at $260, I can do it in 30 minutes.

 

For less than $10 can know if your IAC is good or not:

https://www.youtube.com/watch?v=JfGa3hFSg7U

https://www.walmart.com/ip/Dritz-T-Pins-40-Count/48647573

 

Good suggestion... Definitely checked this off the list though. It did cross my mind....

 

Awesome, thanks! I have a multmeter so will check it out. Interesting post... will reach through that as well.

 

Yeah, that seems a little steep. Hopefully that was at least for a genuine OEM part, lol...

Only good thing about that is that you aren't going to pay for it if that's not what the problem is.

I had an issue with a company vehicle that was having some wiring issue, and the tech kept finding something new that was wrong. If I would have been charged for him doing the shotgun approach, it would have cost a couple grand, but it turned out to just be the turn signal switch (iirc) that was the main issue.

 

Put my original ICV back on, idles much better but back to where I was. Something definitely wrong with the new ICV -- apparently after market junk. Gonna try to return it.

Thinking I might need to have Maxbore refurb my throttle body. There definitely seems to be a little play in it.

 

Chased this same problem for over a year, did too many diagnostics to list, replace everything starting with as cheap as possible. What ended up being my fix was purchasing a new TB with a IAC+TPS from ToyotaPartsDeal. Idles at 700-750 and accelerates like a champ. Pretty sure I had a mix of bad IAC + worn out TB that made diagnosing this issue very difficult.

"One other observation is when I stop from a higher speed, the RPM will bounce between normal (900 to 2000 RPM) like it's trying to idle normally but something won't let it."

This specifically happened to me too, I was almost thinking a brake booster air leak, but problem has gone away as well.

I got the TB for about $400 and it was well worth it. I almost went with maxbore but because of the new Toyota OEM IAC that came with it, it made it a better deal just to purchase an entire new TB.

 

I am guessing the whole time your not getting the PO505 code which will most often trip with a bad IAC valve.

In my case I was getting a High idle because the firewall was cracked where the cable went through causing it to hang up and never a code

I also lube the linkage on the throttle body every oil change .

best of luck

 

Thanks for this! You are right... at $377, this is very compelling if it comes with a new IAC + TPS. Figured I might have to buy a new IAC at $270 and do the Maxbore for $150. Might pull the trigger on this.

My throttle body certainly seems tired so is probably the crux of my issue.

 

Make sure you get the right TB, theres like 4 different part numbers of TB. You'll be happy with a shiny new TB with OEM sensors on it.

 

When you cleaned the iac did you just spray cleaner in it? I've had to break the whole thing down to get it to function right, a lot of crap gets stuck in there. Also people have been known to install the metal gasket incorrectly, leading to vacuum leak and no code, yes one of those people was me, even though I specifically remember thinking to myself only an idiot could put this on wrong....