Vacuum leak..?

So, I've been trying to figure out a low/high idle issue for a while. No cold start enrichment. Replaced IAC, MAF, ect, fuel filter, plugs, wires, tested coils, injectors. EGR deleted. Rebuilt engine about 10k miles ago

I finally found that the brake booster is faulty and caused a large vacuum leak. Plugged it off until I can replace it. Now it cold starts normally and idles within normal range until it gets warm. Once warm it idles around 900-1k rpms. When given gas it hangs for a second. Still seems like a vacuum leak is present. Tested vacuum at the manifold - over 40mg. Been spraying everywhere trying to get a drop in idle looking for a leak but haven't found anything. Any ideas or anyone ran into similar issues?

2000 Tacoma 2.7l 3rz-fe

 

The throttle bodies on these 4 cylinders seem more susceptable to "wear" signs. Grab the throttle bell crank and wiggle it, in, out up down. It doesnt take much.

 

I messed with it today, tried moving it around and no change in idle. When you say the throttle bell crank are you referring to the crank that the butterfly valve is on? I haven't heard that term.

Side info, my fuel trims are ~+1% ST and about the same long term trim at idle. No CEL.

 

Yes, where the throttle cable wraps around.

 

OEM IAC or aftermarket? I had an aftermarket that had a larger air opening and at op temp it would average 900-1000 rpm. Replaced with OEM and purrs at 700 like it should. Chased high idle all over the place in the meantime.

 

After market. Really didn't want to spend that much on oem but might have to. Any good way to verify that's the issue before biting the bullet?

 

Not sure how you could test but….. you can pinch that By-Pass hose running from the air intake to throttle body, that connects to the IAC, while at op temp, and it should reduce rpm. It’s some reading but check these links and you’ll glean a lot of info. The IAC calibration link shows pics of my oem and aftermarket showing the difference in the air opening I’ve already mentioned as well as description of differences.

https://www.tacomaworld.com/threads...from-oem-to-aftermarket.789119/#post-28248267

https://www.tacomaworld.com/threads/iac-tps-advice-96-2-7l-4wd-mt-143kmiles.780248/

https://www.tacomaworld.com/threads/throttle-body-iac-cleaning.819537/

https://www.tacomaworld.com/threads/cleaning-3rz-intake-components.854476/#post-30501082

 

Thanks I'll look into that

 

Getcha a fluid trasfer pump and put a cigar on the input side and pump the smoke into the intake system and see if it emerges where it's not supposed to. It might not show anything at all, but its one way to eliminate the vacuum leak side of things.

https://www.harborfreight.com/multi-use-transfer-pump-63144.html

 

Skip the cigar and use a cheap smoker. They are cheap these days and an invaluable tool for old cars. But I would also be highly suspect of an aftermarket idle control valve.

 

Skip the cigar and the cheap smoker and just find a kid with saggy pants to suck on his mega vape and blow into the manifold.

 

Ok. My point is I have used every hack way of detecting vacuum leaks over the last 40 years of wrenching, and nothing comes close to a proper machine with its own pump. Big leaks are easy to detect with various methods, but they just don't show the tiny ones like a machine will.

 

Update: The truck now will not start and idle on its own. I have to give it some gas until it warms up and even then it idles too low and shakes. I'm suspecting the aftermarket IAC is faulty. Drives fine other than at idle.

 

After reading Thatt's thread....I was a believer

I pony 'ed up for the $300 oem one

eventually they'll stop making these.......then it'll be to lateeeeeeeeeee

https://www.tacomaworld.com/threads...from-oem-to-aftermarket.789119/#post-29171630


I'd be careful about counterfeits on Amazon and ebay

counterfeits have the plastic inserts instead of the temperature compensating spring