High idle problem

I ran this test, as well as probing the ECU to make sure voltages were being sent and received as well. IAC seemed to be working fine. Still not convinced I didn't have an issue with the IAC though...

OP, does your idle jump up and down when you're slowing to a stop? This is a problem I had as well.

 

The MAF should be around 1.7 lbs/min @ 2500 rpm.
The 19% fuel trim has me “guessing” why it’s this high?

 

Thanks tnshooter that will be my project tomorrow evening. I haven’t ran a test on it just cleaned. To answer your question yes the idle jumps up and down then settles in to a constant 18-1900. Funny thing is even when warm when first starting up idles around 12-1300 then slowly raises to the 18-19 range within 30 seconds

 

Alright, save yourself time and money by just replacing the Throttle body with new OEM sensors You're problems seem to match mine, and you're headed down the long b road I went by testing everything (which isn't a bad thing) but not coming up with anything conclusive. I'm willing to bet it'll solve your issue

 

Thanks for the info guys!

 

B1S1 shows a slightly lean (15.3:1) AFR.
and the B1S2 is dumping fuel at 99%

At least that’s how I’m reading it.
And I’m not too good at reading these things. Maybe someone more qualified and knowledge can help out?

Then again, I thought B1S1 did most of the fuel work?


Help. I don’t really know what to make of it?

 

Hey I’m having the same issues, definitely give this a try before replacing the TB! Also I would recommend double checking the IAC valve, make sure the gasket is properly seated, hope this helps!
https://youtu.be/_S9B3IhK_Tc

 

blackstallion, did this end up working for you? Seems like it would be more likely to work on newer, electronic throttle control vehicles.

 

1.1 pounds per minute translates to 8.3 grams per second. Spec at idle (650-750rpm) should be between 5-7 grams per second. You’re at 8.3 grams, but that’s reasonable considering that your rpms are higher.

So because the amount of air is read by the maf sensor, that rules out a major vacuum leak, because the excess air is getting in through the intake. To me, this all points to idle air control valve being stuck or broken and remaining open, making your idle high.

So what about what happens when the truck warms up? Well, here’s my theory based on my limited experience:

When the truck first starts up, the ecu runs in whats called open loop mode. This means that it ignores the sensor data from the 02 sensors and more, and runs according to factory set fuel map parameters, taking input from stuff like rpm and tps. Basically it assumes everything is running as designed. This is in part due to the fact that some sensors need to be warm to provide accurate data. Once the truck is warm, three things happen: the iac should close, the ecu changes to closed loop, and it starts using 02 sensor data to adjust fuel trims.

in your case, the lower rpm during warm up is your truck ignoring to the 02 data. It’s been putting fuel in as programmed but once the truck warms up, the idle air control valve is supposed to close. When it doesn’t, there’s more air than expected, which causes the 02 to tell the ecu to dump in fuel, causing your raise in idle and stft.

you can check the open or close loop status using the scan tool. Someone else please check the logic here, I’m gonna check in later.

 

Rastopher, yesterday I did this process multiple times, by the 4th time (waiting 5-10min each time) the truck actually lowered it's Rpm's to normal 750 range! But once it did I noticed it didn't have a healthy sound at Idle, even though the RPM's were normal. I then test drove it and the RPM's jumped right back up to 1500-1900 range. Today I took the throttle body off to clean the IAC Valve again and noticed I put the Throttle Body gasket on backwards! I flipped the metal gasket around and put the throttle body back on and sure enough, the truck idled high until warmed up and then dropped from 1900 all the way down to 700 as the ECU re-corrected it. Just got back from a test drive on the freeway and the truck has no more idle issues! PRAISE THE LORD!! So, my recommendation for you is this: 1. Check for any vacuum leaks, 2. Remove Throttle Body and replace gasket ($2.00 part), 3. Remove IAC valve, replace IAC Gasket ($3.00 part), and clean that sucker really good with Throttle Body Cleaner and ear swabs! Follow the steps in that video for resetting Idle after any change you make. I hope this helps man, if you want really good instructions on cleaning IAC or removing the Throttle body check out this video: https://youtu.be/agIRNNA-6cs

Also this is where I bought my parts, cheaper than other places I compared (even Amazon), it allows you to type in your make and model of vehicle. I would order 1 Fuel Injection Idle Air Control Valve Gasket, and 1 Fuel Injection Throttle Body Mounting Gasket: https://toyotaparts.mcgeorgetoyota.com/

 

Well Guys, thanks for all the input. Finally running right... ended up replacing the IAC and she is running good! Again thanks for all the help

 

Thanks for posting the solution! Glad it worked out.

 

Glad you were able to get it done.

 

Did you end up buying just the IAC, or going with the new TB which comes with all new sensors? I have the same issue as you had. Issue arrived after VC job and cleaning out the NASTY throttle body. Cold start idle is 1100, then rises to 1900 at warm engine idle. I'm kind of in the middle of doing all the diagnostics now, but kinda just wanna throw a new TB and sensors at it and be done (hopefully). Once I discovered the high idle, i took the TB back off again and cleaned the IAC, but it is super gunked up and i'm not sure that I could get it clean enough.
When the IAC comes off the TB for cleaning, should it be in the open or closed position? Mine seems to be in the open position, and I'm wondering if that is normal. I guess I need to just test the dang thing, but worried I will just get confusing data and still be in this rabbit hole of diagnostics.
Anyway, glad your truck is running right now, and any help is appreciated!

 

One thing you could try if you have more time than money, is buying a super cheap $25 iac from Amazon. If it works, you confirmed the issue and you can buy a real part. If not, it’s only $25. In my experience, my original oem iac stopped working after i cleaned it as you described.
also check this video for how to test it if you want.

Let us know what you figure out.

 

That's a good idea. I'll probably end up doing that. To test the IAC seems like a pain and I don't even have the right tester leads for it, so I might as well buy cheapo part (for now) like you said. So far, no vacuum leaks (that I know of) and no CEL. Truck runs fine once in gear, but P and N stay at 1900, even after battery reset and driving some miles.
First, I'm gonna try these things next.
-Change out the spark wires. They hadn't arrived yet when I did the VC job last week, but they just arrived. I don't think this is my issue, but won't hurt to replace them since I was going to anyway.
-Inspect the TB yet again, and look more closely at linkage, bore wear, plate angle, etc. Also, I will manually throttle it and see if my idle will decrease at all.

Is there supposed to be ANY gap at all inside the TB around the plate? And what is throttle plate position supposed to be when truck is off vs when it is cranked on and at idle.
Thanks!

 

Throttle should be closed completely at idle; you should not be able to use your hand to close it further than its resting position. If you can, it needs adjustment using the adjustable screws.

 

You need to separate the two parts of the iac to properly clean. Most tutorials just show you how to clean the upper part of the valve, that will work if it's not totally gunked up, otherwise you need to separate the plastic portion.

 

Ah, I was wondering about this! When I cleaned it, I was nervous to do that, bc I wasn't sure if that was ok to do. Plus, like you say, none of the tutorials/videos mention it. At this point, it's definitely worth a try. I'll do that tmrw. Also, I'm gonna look and see if the TPS is one that can be adjusted. I finally got my scan tool to work tonight, and I took in for about 50 miles to glean some info. (I don't really know what much of it means yet, as I'm still learning). I did see that the throttle angle was around 8.2. Is that too low? I've read on TW somewhere that the range should be 9-12, ideally at 10.

 

I think most don't want to take it apart due to the sealant over the screws, that's all it is, just rtv. I've done it twice, once where I bought it and last year when I was having issues and the simple cleaning didn't fix it. I'm the wrong person to ask numbers, mechanical things stick in my brain, but numbers never lol. I've got a sheet somewhere but can't find it.

Another thing to consider, doubt it's your problem though, i was chasing bad mpgs, poor throttle, etc, tested/cleaned sensors etc. Narrowed it down to o2 sensor or bad cat, pulled em and both were good, but the gaskets on the exhaust were gone. There was no evidence of an exhaust leak, but swapped in new gaskets and I'm getting mid 15 mpg vs mid 9....