Sporadic idle after cleaning throttle body

INFO:

• 1996 Tacoma 2.7l 3rzfe Manual 4wd
• no tools to read RPMs, so no specific information regarding that
• Cleaned TB to fix rough and low idle when starting the truck
• apologies if I’m doing anything wrong, I’m new

I’ve been having excessively high idle after cleaning the throttle body the previous night. I took the TB off, as suggested, and I cleaned it thoroughly. I also cleaned the opening of the intake manifold just to make sure id get the best performance from the cleaning. One important detail I missed, however was the TB gasket. I ended up buying a gasket material sheet and making one myself which later tore during the installation, but I still kept it on anyways. During the installation I lost one of the TB bolts in my engine bay so there are currently 3 bolts holding the TB on. Also, the screw that usually touches the dash pot on the TB no longer touches it. I made sure to reconnect everything just the way it was, but when I cranked it up that night, the idle was a tad higher than it has ever been.

when I cranked it up today, however, the truck started right up like everything was fine, but as soon as I would put it into neutral the engine would stay revved up like I’m still pressing the gas pedal. In one instance I was going 50~55 and put the truck into neutral and the engine stayed revved like I still had my foot on the petal. Pressing the gas and revving the engine returned the idle to “normal” aka the tad bit higher idle. After driving for another 3 minutes the idle returned to a somewhat normal state but still was higher than what it normally was before. The engine sounds as if the pedal is being lightly pressed down. This all happened on my ≈11 minute commute to school (almost 4 miles)

OVERVIEW:

• High Idle
• Engine stayed revved in one instance
• TB only has 3 bolts holding it on (going to buy new one very soon)
• Home made gasket tore but still installed (going to buy new one very soon)
• Throttle isn’t hitting the dashpot on TB

when I get out of school I will check all vac hoses and make sure everything is connected right and I will also disconnect battery to reset the ecu

How do I fix this problem?

 

Well first step should be pretty obvious: complete the job properly. Get a proper gasket (one that's not torn!) and find that bolt.

Then, if that still doesn't fix it, you probably just need to reset the ECU. Over the years, your truck has learned to deal with a dirty TB, now that it's clean, you're not getting the right fuel/air mixture. Disconnecting the battery for 30+ seconds should help with that.

 

A high idle at startup, until the engine has reached operating temp is normal.

Fix your mistakes before attempting to address anything further. An under torqed tb, with a compromised gasket, isn't the most ideal situation to diagnose high idles.

If you've had the TB off, you've also introduced the possibility of not having the throttle cable set correctly.

 

Do you know if I could buy a new bolt from a hardware store or autozone? I read that the bolt is an m10 x 1.25. Is that right?

 

I have gotten most of my hardware from Ace. They have tons of metric hardware. All the way up to grade 10.9. No need to spend $8 on a bolt from the dealer, lol.

But I would do your best to find that bolt. Random pieces of metal rattling around in the engine bay generally isn't good.

I don't have that size memorized, but that is a common size. If you really can't find it (look in your skid plate), then take one of the others off and take it in to match.

 

I don't think I have seen longer bolts like that at AutoZone before- ACE might be a better bet if you have one around you (I know they are increasingly harder to find). But no matter where you go, I'd bring the bolt in to check the size. m10 sounds too big. m6 or m8. m12 roughly = 1/2", so m10 roughly 3/8, m6 is roughly 1/4". maybe 100mm long (4")... Or did you lose a nut?

I'd also emphasize finding the nut/bolt if possible.

 

Did the TB on a ‘96 have an IAC? A common problem is people cleaning the TB with the IAC still attached, and all that crap washes down into the IAC through the idle air ports. It causes the IAC to either stick open (resulting in an excessively high idle like in your case) or stick closed where it won’t start and idle properly.

Unfortunately it’s pretty hard to clean the IAC once it’s gummed up, but it would be worth removing and checking. The valve should move freely and snap closed when you actuate it by hand.

 

Just the bolt

yes, it did. I was going to take it off but I was beginning to strip the screws while trying to take it off so I didn’t bother.

 

I have an ace near me. Does anybody know the exact size I need? If I need to I’ll take the other bolt off to see, but I’d rather not risk it falling somewhere like the other one. It’s on the back of the TB

 

Alright, I checked all the hoses and one was cracked, which I will replace, but the throttle hits the dash pot like normal again, so that’s good. I cranked it up just to make sure and it cranked right up and had a normal idle. It didn’t sputter or sound as loud as it did before. So I suppose everything is okay, but I’m gonna be driving it around a little bit today so hopefully everything is fixed and all I have to do is get the bolt, gasket, and hose.

Thank you guys so much for y’all’s input. I will let y’all know if there are any other problems or if they persist.

 

We're suggesting you try to find your original bolt dude. It didn't disappear. Did you even look for it? If it didn't fall all the way out, it's probably sitting on top of your skip plate, just waiting for the opportunity to get jammed into your CV joint and cause chaos.

And what else are you doing that you're worried about dropping a second 4" bolt? Maybe slow down when you're wrenching.

We can't tell you an exact size unless someone has one of those bolts around and is willing to measure it for you. I'm certainly not going to go pull one of mine just for that.

 

well yeah ofc, I will. And also the reason I dropped the bolt was because the space was pretty compact and I lost my grip on it. Imma do my best to track it down tho. Now that it’s been driven a little bit maybe it knocked it down to the skid plate like you said.

 

Just an update: truck is normal again, bolt was found, and gasket is coming in Tomorrow.

I suppose the computer just had to relearn