Fixed my surging & fast idle: Throttle body butterfly repaired by MaxBore

I got a manual transmission base cab 2001 Tacoma 4 cylinder 2.4L engine that was running bad with a surging idle and also a surge in acceleration between gears. The truck has about 206,000 miles. What I mean by a surging idle is how it would rhythmically idle low at a less than 1,000 rpm and then surge to about 1,500 to 2,000 rpm. When I drove it the truck would surge in acceleration when shifting between gears.

The first thing I to correct the problem was to thoroughly clean the idle air control (IAC) and the throttle body with carburetor cleaner and a rag. The throttle body was gummed up with a bunch of slimy gooey dark crap. Although I cleaned it pretty well, it did not fix the unsteady and surging idle. In fact, it idled faster. So the next thing I did was buy a new idle air control (IAC), which did not fix the problem. After that I cleaned the mass air flow (MAF) sensor and it did not help so I put in a new one. This was also to no avail, so I also sprayed carburetor cleaner on all of the vacuum hoses to look for a vacuum leak, which I did not find any. I then put the truck in two auto repair shops and multiple professional mechanics could not resolve the problem. The truck was now idling at about 4,000 RPM!

After all this I was about ready to give up and then I examined the throttle body butterfly and noticed that there was a significant gap around it, which probably explained why it was idling so fast. [Yes I cleaned the TB pretty well, but my cleaning removed a ring of gum around the butterfly that was limiting a lean air/fuel mixture.] I was tehn tempted to buy a whole new (used) throttle body, but a replacement was about $150 and did not look much better than what I already had (dirty & gummy butterfly valve).

I then discovered a website called Maxbore.com that re-bores throttle body's and fabricates a new butterfly valve for any TB.

Any way, I shipped my throttle body to this Maxbore guy in Florida and he re-bored my throttle body and made a new butterfly valve for it. I got the TB back today and installed it and the fast idle and idle surge problem is now resolved.

I'm passing this information on because this whole ordeal was very costly for me because I bought parts that I did not need and paid for mechanics to help try to diagnose the problem, which they failed to do. All I really needed all along was to send my TB to Florida for repair, which took less than a week and cost a total of $125.

Enclosed is some photos showing the before and after TB butterfly.

 

That's badass hombre. Thanks for posting that up.

 

This sounds exactly like what I’m dealing with. V6 auto, but constant high idle and some surging. Idle will sometimes drop when engine is reved around 5000 rpm. I didn’t even think to check this when cleaning and then replacing the iac. Great post. Hopefully this is my issue.

 

Looks like nice work.

 

Nice... was cleaning my TB and MAF sensor today as well. Good to know that guy is out there

 

I bought a 2001 2.4L a couple of weeks ago, with these idling issues. I put the VIN in at Toyota (https://www.toyota.com/owners/parts-service/history) and it showed Engine Induction Service having been done last year at the local Toyota Dealer (this left me thinking [my bad] that last years cleaning had taken metal off with the carbon). I was leaning toward the butterfly valve in the TB after a couple of weeks of searching & mulling (ouch!), but my mechanic said he'd better look at it. It was indeed the IAC and I paid for a new one. My truck now idles at 500 rpm. I feel a little bad for the last owner. He had done an EGR Delete for some reason; perhaps out of frustration with the idle issue. My mechanic said that the TB and IAC didn't look like anyone had ever cleaned them at all.

 

Did this years ago on a 22re yota, made power or really just got it back tbh. I need to do this on my 5VZ now.

 

I wonder if there is any increase in power with the added 3.5mm bored out throttle body.

 

Yes absolutely! Though with anything bored over, the air can’t be restricted beyond the ported side so Max Bore really wants you to send in the intake plenum to match the bore size and gasket. I did it on a 22re manual and it was n/a the truck would really get it on as with ported heads. You’ll feel it on the butt dyno especially with a supercharged meth setup.

 

Haaa, got it, well that would mean sending in the supercharger then because the throttle body connects to it and that’s probably more hassle than worth it, so the new larger butterfly does not hit the plenum side?

 

Shit! I forgot, you could bore it but thats a whole rebuild I don’t think you would want shavings..

 

You just helped me so much. I have a 5vzfe. Been chasing down high idle, thinking it was computer or sensor related. Saw this, pulled off my throttle body cleaned it, dirty as hell, and sure enough same exact thing.

 

Many thanks for this, o4Taco.

My '99 2.7L manual trans suffered a similar idle inconsistency problem. A real pain in the a** first looking for vacuum leaks, checking the TPS, IAC, lubing the butterfly door axle, etc. All pointless aside from the resulting reassurance that none of that stuff is out of whack. So, I sent the throttle body to maxbore.

Idling now at exactly 750 rpm. Amazing. It's been three months since installing the fixed throttle body, but I still can't help looking down at the tachometer when at idle. Brings a smile to my face every time.

A plus worth mentioning: George at maxbore is a cool guy. Easy to work with. Good communication. I experienced a fast turnaround time.

 

I changed the iac,and tps, and cleaned the t.v. because it would start then shut down,tryed starting it and it took for ever, had to keep pumping it then I would run pretty good but know it fluctuates and idle higher,
Thing the fuel pump might be on its way out or my fuel injectors going bad

 

Had the throttle body bored and everything works excellent

 

What else did you change, besides bored out tb

 

I had the standard maxbore service done to my throttle body,

I had the supercharger ported polished three or four months ago

 

Supercharger is for 2.7l or v6

 

V6

 

Hey OP thanks for the recommendation! I have been having idle issues ever since cleaning my TB after doing valve cover gaskets.. I really didn’t think I did anything wrong- actually thought I was doing the right things by cleaning TB and IAC but truck has never idled right since then.

Is there any way to know you need this done? My butterfly valve definitely has a gap around it... maybe not as extreme as yours did but close. Is it supposed to be tight all around?

Thanks