I have a subtle 50 rpm fluctuation. Its almost like a cycle of some sort.

I just went and replaced every hose known to man and it still didn't fix the issue.

Has an aftermarket IAC valve been known to causse similar issues and not necessarily the common failure but just poor operation in general? The PO put one on as I am guessing he was having high idle issues which is the common problem with a bad one.

I now I have a really odd hesitation whenever i barellyyyyy touch the throttle. I just noticed this when I'm park a few moments ago.but whenever I actually give normal throttle there is no problem.it will bog down to below 500 rpm, it won't die, and when I give it more gas it revs on up properly.

Before I swapped all hoses it drove well. it drives good. No misfires or anything. It gives me zero issues under load or regular driving conditions.

Bare in mind I've already down plugs, coil packs, 02 sensor, still haven't done MAF....but I'm more inclined to believe if it's OEM it's not casuing the problem.

Just hoping someone has had similar experience becasue I can't find anything on it

Help me cure my idle wooes.

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Have you checked for intermittent air intake leaks? Meaning along the rubber hoses between the air box and intake runners?

The rubber piece closest to the runners on mine had a crack that would cause some hesitation, replaced with OEM and it purrs like a kitten now.

Luck and enjoy the Runner!

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that was actually one of the first things i replaced. I ended up putting an airiad neck on their instead.

I gone through it tooth and nail for any more hose leaks. I even put together a smoke machine and pumped it into the manifold. That helped me find a few of my initial bad hoses as well. Now for shiggles i hooked it up again and now i got no smoke coming out.

but still got the idle issue lol I was really hoping it was the vacuum leak causing it since it was subtle.

Also to note i have already replaced the PCV valve. Everything ive been putting on has been OEM

I’d be willing to bet that it is the aftermarket IAC. My buddy when he had his 4Runner back in 2010 went through three aftermarket ones in the process of a year before breaking down and spending $130 on a new OEM one. We tried to adjust the plunger twice to no avail, unfortunately. Probably could get one out of a yard for dirt cheap.

Tested the TPS?

Your slight hesitation is not normal.

It could be the IAC.

Can you read live data? If so look at your TPS. It could be found bad and have a fluctuating position at or near idle.

If you are running an aftermarket air filter I’d clean the MAF sensor with MAF sensor cleaner.


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I tested the TPS a week or to ago. But not under that specific condition whenever im feathring the throttle like that. I suppose I check it out again under that. I'll report back

I can't go cruise around in it yet until I get my rear axle seal's and axles fixed with new shiz. Which means all i can do is keep in Park and rev engine lol.

I was looking at IAC on a junker this weekend....but FSM says not to clean it. The engine it was coming off looked pretty dogged. I may just fork over the money to get a new one.

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I will check the TPS again whenever I get a chance. Will be a few days I'm rebuilding rear axles today and today. (lucky me). I'll check it again after that's done

Everything on the air intake is stock, heck I just dropped in a new OEM filter. Only thing that is different is the tube after the MAF is airaid.

I did notice two very small pin wholes in front of the filter before the air gets sucked into the filter....but that couldn't be causing the issue...and not to mention the two pin holes are in super odd spots. They are super tiny. Maybe 1/16th of an inch or less in diameter

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No problem here having cleaned two OEM IACs rather throughly. Used Valvoline carb cleaner. I took a long skewer to clean the plunger. It isn’t like the TBs of today, where you need a scan tool with recalibration capabilities if you take them off to clean them.

TPS is the issue. I had similar issues in my corolla at idle. RPM went up and down and later replaced TPS and problem solved. Use OEM parts.

I tried the junkyard route once when I needed a spare throttle body. It idled terribly and even stalled on me, in an auto. I would stay away from junkyard IAC's since they tend to get real sticky when they sit a long time or something.

Okay so I'm driving the 4runner again got my seals done.

So alittle more backstory not sure if I mentioned this, but the battery was pulled for like 1 hour before I cranked it back up whenever I FIRST ran into this issue and posted the thread.

So I crank it on, idles fine. Doesn't go above 1k oddly enough. I put it in drive, and you can feel the stuttering when I feather. I give it more gas, stuttering gone.

I get to a stop sign, and I have to climb a slight incline I give it a small amount of throttle and sure enough it dies. I crank it back up mash the pedal and it drives.

I drove it around on highway and back roads for about 50 miles yesterday. And oddly enough, it seems driving it fixed it? The problem does not exist anymore.

I did not have my scanner on me. I will grab it this morning before I go to work and see if I can drive deeper in it.

But based on those symptoms Alone it does sound the TPS

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As engines get old they require different parameters to operate than what was pre programmed into the ECU. They are called adaptive parameters. When you disconnect the battery the adaptives go away and it’s stuck with default parameters.

Driving it around a little allowed it to relearn it’s idle parameters and its fuel trims.

What does your TPS position read at idle and wide open throttle?


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fortunately you own a year where the TPS can be replaced easily with just two screws ( where starting in 2001 you had to replace entire throttle body $$$ ).
If your idle condition persists, I would try a new one, wont hurt, and they do wear out.
While for me idle issues were the ICV and I did clean it and fix it, months later I had a flat spot in accelerating, no codes, replaced TPS and prob gone.

So i am only able to measure absolute throttle position. IIRC that is related to the TPS where it takes the volage and converts it to a precentage.

so idle its at 9% when i feather it i saw it drop as low as 7.5%. then whenever i was acelerating it was climbing it wasn't one set value. I think i got to 72% before i backed off because it started at 60% ish then i realized what it was doing and backed off. dont want to go 100mph down the high way lol

When you feather it I’m assuming you push it a little. Is should not go lower than your idle position. My idle position is 11% and wide open is around 72%

An easy way to check it without going 100mph is just turn on the ignition without starting it. Then watch the tps position from idle to wot as you depress it slowly. The percent should slowly increase and not decrease.

I would say replace your TPS sensor.


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