Throttle Body for 97 Tacoma

My shadetree mechanic has diagnosed my high idle problem to a worn-out throttle body. I have a 1997 Tacoma 2.7 liter manual transmission 4x4 with 263K miles. We are trying to avoid a brand new throttle body from the Toyota dealer in order to save some money. My mechanic has searched multiple local junkyards and has done exhausted online searches with minimal luck. He advised that the first generation Tacoma's are scarce in the salvage yards. The few used throttle bodies he located were beat up, overpriced and had no return policy. Are there any online suppliers that are reasonably priced and offer a good product that you can recommend. Open to ideas.

 

You can get yours rebuilt. Max Bore is a company I believe has been recommended before @1997tacomav6

 

Maxbore will rebuild it for around 150.00 and that will fix your problem.
It took a few weeks 1st come 1st serviced.
Bored out with a new shaft and butterfly
http://www.maxbore.com/

 

Thanks for the info on MaxBore.com! I will be contacting them to see if they can possibly help before I ship the TB to them.

I did some further troubleshooting. I noticed when the engine is turned off the TB closes fully, but when it starts and idles (even when fully warm) the butterfly valve is slightly open (presumably causing the high idle). I did confirm that the IAC plunger is not pushing the butterfly open. This would make sense as my mechanic already replaced the IAC and TPS. I even disconnected the throttle cable to eliminate that as a possibility.

I removed the Throttle Body and noticed that it seems to close fully. I can hold the TB up to a light and see no gaps in the intake, so I am at a loss as to what could be causing the butterfly to open on its own when the engine is at idle. Is it possible that the vacuum from the engine intake is opening the TB (due to a weak butterfly valve seal or maybe a worn-out return spring on the valve)? Again, the valve seems to close tight with no gaps when I removed the unit and inspected it. This is beyond annoying.

 

I've heard a bad coolant temp sensor can cause high idle.
There's 2 temp sensors.

 

I talked to MaxBore.com and advised him that I removed the Throttle Body from the intake and noticed that it closes fully (I could hold it up to a light and see no gaps thru the butterfly). I sent him pictures of the Throttle Body he verified that there was no gap around the butterfly, so he confirmed that sending him the TB unit to rebore would not resolve this high idle issue.

I went on to explain to Maxbore that the butterfly valve closes fully with the engine off but once the engine is started and idling the butterfly opens slightly on its own (even stays open when engine fully warm). When I told him that I was unable to manually close the butterfly valve (throttle pulley) while the engine was at idle, he recommended I begin disconnecting vacuum hoses one by one from the TB and manifold. Then plugging the connector with my finger to see if the idle drops or stays the same.

Per the attached pictures, the one with the red arrow show the butterfly open when the truck is at idle. As you can see the plunger is not causing the throttle to stay open. The other picture without the arrow shows the engine off, and as you can see the butterfly closes all the way against the stop screw and plunger. From what I can tell there is vacuum pressure somewhere in the system that is causing the butterfly to open on its own.

Let me know if anyone has any further insight.

 

Can someone on this thread with a Gen1 Tacoma 2.7 liter verify if their throttle butterfly is completely closed at idle (fully warmed)? Please reference the pics in my above post for details. I have read conflicting information as to whether the throttle opening slightly during warm idle is normal.

 

I have a 1998 3.4 and I had a somewhat similar issue. To solve my issue I just sprayed the shaft with WD40. I think what's happening is the springs might be worn and/or there is to much friction on the shaft to hold it closed but engine vacuum is probably pulling it open a bit (as you suspected). I don't know if the shaft is lubricated at the factory (I'm guessing no) but in any case try spraying the shaft with WD40 to see if it helps. If it does it will likely be temporary. Probably need to completely disassemble and clean the shaft but I have not tried that. My TB is ridiculously complex, springs on both sides of the shaft, mech dashpot and vacuum dashpot.

Be aware though that the vacuum dashpot in your picture is compressed at idle. When you push on the throttle while idling does it move easily to touch the dashpot?

BTW I assume you know this - the vacuum dashpot seems to be designed to keep the throttle slightly open before starting, I suppose to get some extra air on initial firing and then of course it closes on vacuum to allow proper idle. I'm guessing that sitting most of the time at the slightly open position it somehow gets stuck there - likely weak springs or friction. Mine is the same, the parts are just different locations on the TB.

Another cause of this is that the shaft is able to move on its axis and the butterfly gets hung up on the side of the TB bore. I saw a little of this on mine (wear on the inside of TB where butterfly rubs it) but it did not seem to be the cause. Check for rub marks inside the TB, when people see this they send to maxbore because that's only way to correct it.

 

Per the above post from alexh and my other research I am beginning to believe that the butterfly valve opening slightly during idle may be normal. I removed the Throttle Body and recleaned it then lubricated the butterfly shaft for good measure (although the TB was pretty clean and seemed to open/close without any restriction and with decent spring tension before that).

When reattaching the TPS I noticed that when the TB is completely closed the TPS bolts onto the assembly in the default position of being about 5-10% open. I'm not sure if that is by design as I would expect the TPS to be completely closed when the TB is completely closed so the minimum voltage could be sent to the ECM. I am pretty sure that the TPS my Shadetree mechanic installed was aftermarket. (Not sure about Toyota's but I know Honda's don't idle well with aftermarket TPS's).

I reassembled the TB and installed it leaving the TPS off the butterfly but plugged in for testing (so the butterfly wouldn't automatically cause the TPS to turn so it would be at its minimum voltage). By doing this I was able to get the RPMs at warm idle to drop from 1500 to 1000. Per the attached picture you can bump the idle up by manually turning the TPS with a screwdriver.

At this point I am thinking the high idle may be electrical or sensor related and not mechanical or vacuum related. There was a previous post above referring to a faulty coolant temp sensor, so I may explore that next.

Any further ideas here?

 

I was not really clear in my post, but what I should have said is that the vacuum dashpot does not set the idle, the position of that dashpot is not accurate enough and its way to far from the lever at idle. Its just to provide extra air on initial startup and then it pulls away from the lever, assuming its the same function as mine. There must be a adjustable stop somewhere else that sets the throttle position when idling but it usually has loctite and paint on it and you are advised never to change this.

You should locate this stop and make sure that the part that rests on that is touching. For mine I could slip a feeler gauge between the stop and the part that rests on it and when I pushed the throttle back the idle went down. Why mine does not rest on it, not sure but wear, dirt etc.

I think the critical question is - if you push the throttle lever to close butterfly does the idle decrease? If so its probably mechanical, if not electrical. And to tell the truth most high mileage Tacomas have both a mechanical problem and a dirty IAC. When I clean my IAC idle goes to normal but not for very long probably because its difficult to clean thoroughly.

I had to look at my TB for quite a while when off the truck to figure everything out , its very complex. Actually for the 3.4 you cant close the butterfly completely off the truck unless you have a small vacuum pump attached to the vacuum dashpot because it has a really strong spring holding throttle slightly open and I could barely push it with my finger. When I was able to apply vacuum to the dashpot I also saw my butterflys were tight in the bore.

 

Update: After much research I was able to find a new genuine Toyota throttle body online for $352. I figured that was a pretty good deal since that price included the TPS and the IAC already installed on the unit. After installing the new throttle body the warm idle dropped from 1,500 RPMs previously down to 1,000 RPMs. The truck also idles more smoothly on cold starts. I realize that 750 rpm is ideal (especially since the manual 5-speed shifts better at this idle) but 1,000 rpm is much better than before.

I may try an ECM relearn to see if that resets the idle to 750rpm. Aside from just unplugging the battery for 20 minutes, is there a better method of doing this? I've read that some Toyotas will reset if you turn the key to the on position a couple times without cranking the engine (while modulating the accelerator pedal thru its motions), then start it. Since this is a 1997 it may be too old for some of these tricks. Any other suggestions here?

 

I didn’t know these were even available,
We’re did U buy it from?

 

The cheapest places I could find Throttle Bodies were:

1) oemvehicleparts.com
2) toyotaparts.bochtoyotasouth.com

I went with option 2. They shipped the unit to me within 3 business days.

 

Truck running well but still idling at 1,000 RPM. Was able to temporarily get the idle down to 750 by doing the following:

- Getting the engine warm, then turning it off.
- Turning the key all the way to the on position without cranking the engine.
- While in the on position with the engine off - slowly pressing the accelerator all the way open then slowly releasing.
- Repeating the above step again.
- Starting the engine.

After going through the above cycles the truck idles at 750 RPM like it should but once I start driving it goes back to idling consistently at 1,000 RPM.

At this point I would guess this is an electrical issue. Perhaps the ECM is causing this? Aside from disconnecting the battery is there a better way to do a hard reset on the ECM? Maybe a high end scantool would do this?

 

Again, if you are idling and push the throttle lever on the TB to the closed portion does idle decrease?
Also, check the TPS according to spec in FSM for correct idle position resistance or some have a dedicated switch in the TPS to signal idle.
If the ECM thinks you are pressing on the gas it will not adjust the IAC.

 

I have tried pushing the TB closed while the truck is idling but it would not close any further (perhaps the vacuum is too strong to allow it to close when the engine is on).

I can check the TPS as you suggest, but the throttle body (along with TPS) is a new OEM Toyota part, so I would be surprised if it was defective.

 

What is the benefit to have the TB bored out?

 

Based on my research the boring out of the Throttle Body provides some performance enhancement. It would also alleviate issues with the butterfly as MaxBore also re-machines the butterfly for a tight fit after boring the TB. My situation is a little different as I am just attempting to correct a high idle. I talked to George at MaxBore and explained my situation to him. After sending him pictures of my throttle body showing that the butterfly closed tightly with no air gaps, he concluded that boring out of the Throttle Body would not remedy my idle issue. Per my previous post I ended up ordering a new OEM throttle body (which thankfully included a new TPS and new IAC). This mostly fixed the idle issue as it previously idled at 1500-1800 RPMs before replacing the TB. It now idles consistently at 1000 RPM. (750 is ideal but I will take what I can get).

 

like mentioned above, over time the inside of the throttle body gets worn out by the butterfly and creates a gap that lets extra air through and causes idle/performance issues. Getting it rebored corrects that issue

 

Getting your TB bored BIGGER fixes that issue? Interesting.