An.Idahoan

Ubermoto - I'm glad I read through this whole thread. There's some good ideas on here in the way of not-so-routine maintenance I should try on my truck. I'm thinking of taking my IAC off to clean it and since you swapped yours with another I figured you'd be a good one to ask how complicated that gets.
Did you have to drain the coolant?
Was the inside of the coolant passage gunked up?
Was there a way to limit how far the IAC opens? I'm annoyed at how high it idles when cold. 1700rpms is excessive. If there were a way to mod it to limit air flow, I'd go for it.
What opens and closes? Is it like the butterfly in the TB or a diaphragm or what?

eddieleephd

I must restate that when you do this the air must be removed from the throttle body. The way I did this is by following the coolant line towards the rear of the engine where you find the soft line meets a hard line. Here you will find a clamp that can be removed with a pair of needle nose pliers, remove the clamp and twist the hose to free it and make it easy to pull off. Then start the truck and remove the line for as long as it takes to have a steady stream of fluid come out and put it back on. This is to be done after the IAC cleanse.

" The IAC is a temperature gauge and if air is in this it will have a high idle as some are stating as well......"" so this may be the first issue in the first place sometimes a better place to start!!!

I did do this as well and you have to remove the throttle body to do it I think it took me about 45minutes. including the TPS..

SuperChargedTaco28

Hi all,

I just wanted to share the answer with everyone as my Supercharged 2002 Taco 3.4L went through the exact same thing 6 months ago. It was caused by Goodyear cleaning the TB, and I actually ordered a new TB to fix the idle issue 1 hour before my friend fixed it. The problem was the butterfly valve not closing all the way. The solution was the rear striker plate was causing the front one not to close. There is a dashpot on each plate, but the one in the rear had vaccuum stuck inside and would not close. As soon as the vaccuum was removed, in my case with a super charger, I had to remove a cap on it, you may have a line. As soon as we did that, the throttle closed completely, sprung back when you let off the gas, and idle came back to 750! Hope this helps someone.

Swede

I'm in the same boat here too. High idle and crappy mileage. I've done everything that I can think of and still the same thing, 1700 rpm after she's all warmed up.

Vacuum lines - All good
MAF - Spec's all OK (and cleaned)
TPS - Spec's all OK (idle's @ 9% WOT @ 75%)
ECT - Spec's all OK (steady 88c)
IAC - Spec's all OK (and cleaned)
Cables all have a bit of slack in them.

I'm starting to think that there is something wrong with the TB itself but there isn't any play in the rod or linkage anywhere either. So frustrating!!!

DRCOFFEE

This worked for me. I did the whole maintenance thing last Spring and cleaned the TB with cleaner and it was too late before I noticed all the liquid and crud pouring down the hole in front of the butterfly valve. DOH!
As soon as I started the engine, i had the high idle. That hole leads to the IAC valve and all that carbon just gummed it up, keeping it wide open.



My (painless) solution: I got my truck to idle again. I ended up pulling off the plastic intake tubing and gave a couple of squirts of MAF cleaner down the hole in front of the throttle plate. I left off the plastic intake tube and started the engine and it fired up and then died. I did that 3 times, each time hitting it with 2 quick shots of MAF cleaner. What I was hoping is that the cleaner would dissolve the carbon and then suck it past the IAC valve letting it function again and close. I was right. After reconnecting the plastic intake tube it fired up and the idle dropped to 750. I didn't have to remove the IAC either. Don't flood the hole, just two quick shots of MAF cleaner should dissolve any crud.

The reason I used MAF cleaner is it doesn't leave a residue and is less aggressive than carb cleaner. Don't ever use brake parts cleaner.

I hope this proves to be an easier fix for this problem than removing the throttle body.

This is the inner workings of the IAC. On the right is the valve. Carbon can stop the valve from closing, letting too much air past the throttle plate.

eddieleephd

I agree that the butterfly valve is not closing fully. I did have to clean the TB to solve this same issue. once I could get that slight opening to close completely issue was solved and resumed correct idle.

Swede

I finally cured my high idle issue and I'm pretty sure a lot of you are having the same thing happen. I don't mean to hijack the thread but the details are here: https://www.yotatech.com/forums/f2/m...-cured-258318/ Hope it helps guys!

zipposrule

did you ever figure out your problem? i am having similar issue with my 95 taco with the 3.4l and have given up. any luck with any of it?

Swede

Updates?

jaretstuff

I'm getting 1300 in my 3.4 T100 and it's making me mad

An.Idahoan

Hey Swede,
I last replied to this thread nearly 3 years ago. I was thinking of modifying my IAC to limit the high idle to closer to 1200, but never got around to it. Since you've had your eyeballs down inside one of these, would you have any recommendations on how to do that? I figure there's got to be a ledge or stop somewhere in there. It'd be nice if I could put a machine screw in from the side to adjust the max range of motion for the valve inside.

eddieleephd

you should try using PB Blaster as I posted previously, as well you should be sure the air is burped from the IAC by removing the line at the back with the engine running at cold temps and immediately replacing it.

eddieleephd

Try both things I posted earlier and if that doesn't work run 2 steps cooler plugs. this made mine idle around 900...
BKUR5ET recommended for supercharged engines.

An.Idahoan

My warm idle is 850-900. I don't have any problems there. My cold idle is as high as 1800 on mornings that are 20F and below. It ramps down normally as the engine warms up. Correct me if I'm wrong, but 1800 is stock high idle on a 95 3.4L tacoma. I see that as an engineering mistake. 1200-1800rpm is just too un-useable for a manual transmission.

I'd like to limit high idle to 1200 by limiting the IAC valve's range of motion and was wondering if anybody here had thoughts on that.

smallfry29

I read a whole lot of threads was looking to cure my code 420 and 402 on a 2000 tacoma with a 2.7L 4wd with crappy gas mileage. Had a bunch of vacumn leaks fixed them made it worse cleaned the MAF sensor replaced the filter in the vacumn switch crawled underneath and checked the exhaust and catalic converter I live in Idaho and this started when the tempature changed still freezing in the morn but warm during the day happened this last Sunday after my husband drove it spent 2 days scratching my head and today I took the gas cap off and cleaned it with a rag and cleaned the opening to the gas tank and wouldn't you know it that was the problem I will be getting a new one LMAO at myself!

Swede

No idea. I never messed with the IAC at all apart from cleaning it up. The only thing that worked for me was the Washer Mod. Still going strong BTW.

83

FWIW, I recently did my valve cover gaskets, and cleaned the throttle body while I was in there. My idle afterwards was around 1200.

I used DRCOFFEEs method, mostly because it was the easiest, and I didn't notice any play side to side in my plate when I was a cleaning the throttle body.

Preliminary results: idle immediately dropped down below 1000. Probably about 800. I'll need to drive it around a bit, but it's been holding steady at around 1200 for two weeks now, but as soon as I sprayed some MAF cleaner in there with the air intake hose off a couple of times, when I connected everything back up and started it, the idle dropped right down just below 1000.

83

Actually I'm still idling high. I did this process again, as well as cleaning my MAF, and resetting the ecu. Idle is sitting right at 1,000 now. I'll give it a few more miles to see if the ecu adjusts before I look farther into it...

sawguy50

Mine had a similar problem and it ended up being the ECU. Had code P0505. Replaced ECU and back to normal.

CK1er

Fuel system cleaner temporarily helps some. Check the shutter, if theirs movement the throttle body needs to be changed. Around $600 through toyota. I found a used one for $130 on eBay. It took care of the issue for my 97 4runner 3.4 L V6.