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Discussion Starter #1 (Edited)
Hey guys, need I your help. I have a 1999 Toyota Tacoma with the 3.4L V6 4WD. Yesterday I took apart my throttle body in order to clean my IAC valve because my RPMs were bouncing anywhere from 500-1700 revolutions. It has been doing this for a few weeks now, but what made me dig into it was the fact that it stalled twice while sitting in a parking lot. Anyways, I cleans the IAC and the throttle body and replaced both gaskets and put everything back together. Today driving it, it the RPMs were would be around 2000 when shifting gears. Then after my 45 min drive while i was parking it was around 1500 RPMs. I tried pulling the wires off the battery to reset things and now the idle is up to 2000. Need help guys, I' at a loss here.

P.S. we replaced the TPS 2-3 moths ago before we figured out I had a bad injector. And while cleaning the IAC, I looked at the MAF sensor and it looks clean.

Thanks in advance
-Kennedy
 

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1998 T100 SR5 2WD
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Welcome to the forums! :)

Did you happen to git any solvent on/in the TPS? Have you hooked up a diagnostic computer scanner to the OBDII port to see what each sensor is reporting? Do you have any vacuum leaks? Have you checked fer a vacuum leak using an unlit propane torch while the engine is running? Is the Check Engine light on? If so, what is/are the exact code(s) being reported? ;)

Disconnect the IAC valve from the wire harness and see if yer condition still exists. Did you happen to fergit to connect something back up? Snap a few piccies of the engine bay and post them, please. ;)
 

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Also, any idea if the coolant temperature sender is reporting correctly?
 

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1998 T100 SR5 2WD
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...and in case yer wondering where the ECT sensor is located:

 

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Discussion Starter #5
I don't think I got anything on the TPS, we did not have it apart when we looked into the IAC. But in case we did, what would i look for? I plant on taking the throttle body back apart tonight to see if we misinstalled something when we took it apart the first time.
I have had my code reader hooked up to my truck while it is running, and it is not showing anything out of the ordinary. I haven't had any check engine lights unfortunately.

I know that I have a crack at the base of a hose going to the resonator?(it's the big black box that attaches to the large air intake hose) but I don't know if its enough to effect it.
I will try disconnecting it tonight to see what happens before we dig into it. We did have everything reconnect but maybe something isn't fully seated? My dad and I are usually pretty eagle-eyed about this stuff but it is a possibility.
I'll post some pics when I get a chance.
 

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Discussion Starter #7 (Edited)
...and in case yer wondering where the ECT sensor is located:

After a quick search, I realize this is what @jcp123 is talking about, right? See that this could possibly be a source of my problems. However, would it cause the truck to stall? And are there any other symptoms that usually help identify a bad ECT?
 

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1998 T100 SR5 2WD
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I know that I have a crack at the base of a hose going to the resonator?(it's the big black box that attaches to the large air intake hose) but I don't know if its enough to effect it.
I will try disconnecting it tonight to see what happens before we dig into it. We did have everything reconnect but maybe something isn't fully seated? My dad and I are usually pretty eagle-eyed about this stuff but it is a possibility.
I'll post some pics when I get a chance.
Um, a vacuum leak will cause a high idle. ;)

Trying doing a vacuum leak test by using an unlit propane torch with the engine running. If the engine revs up, that yer vacuum leak, You could also have other areas so don't stop the test at the first sign. ;)
 

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Discussion Starter #9
Um, a vacuum leak will cause a high idle. ;)

Trying doing a vacuum leak test by using an unlit propane torch with the engine running. If the engine revs up, that yer vacuum leak, You could also have other areas so don't stop the test at the first sign. ;)
Ok so update: we took the IAC back apart and checked everything. After putting everything back together, the freaking thing is now idling at 2500 RPMs when shifting and won't idle below 1500. We were going to take it to a local mechanic but he's booked upped for weeks out. So that leaves it to me to fix it. I'm going to get a new hose for the resonator and replace, see if that does anything.

Also, I noticed right around the same time as this whole thing started, my truck was starting to take a couple extra second to start. I thought battery, maybe, but we put a new one in. So I thought that there might be dots connect here. Could a bad sensor, maybe the ECT, be sending bad signals to the ECM and causing the computer to feed fuel when not needed and back off fuel when it needs it?

Thanks for the help guys, I appreciate it.
 

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1998 T100 SR5 2WD
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Try performing a vacuum leak test by using an unlit propane torch and the engine running. I'm guessing yer throttle body might have a vacuum leak maybe through the butterfly shaft. ;)

Check this video out... ;)
 

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Discussion Starter #11
So update: just dropped it at the a local shop yesterday, will get back to you guys once I have it back. Really hoping its not something stupid that I might have ignored but I only know so much. Thanks for the help guys
 

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Vaccum leaks will not cause a hig idle on a engine with a mass airflow sensor. A map sensor yes. A vaccume leak will only cause rough idle. Give it a couple or warm up cool down cycles to see if it adjusts. Do you have a meter? We can check the iacv. We can check to see if it operates correctly with a jumper wire. Also let it warm up when u have high idle push in on the shaft sticking out of throttle body? Does idle correct?
 
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