Idling at 1500 all the time now WTF?

[Jon]

I know it's normal for the 1500 idle at cold start but it fails to drop down now. Doesn't matter if it's driven for hrs, put it in park and there's 1500 RPM again. In gear at stop lights it idles at 900. It used to idle around 500 in park. Also the MPG's are horrible now only getting 160-180 on a tank. No CEL or any other problems. I've already had my throttle body completely apart and cleaned all the sensors a few months back for a different problem that it didn't fix (long start, bad fuel pump)

This just started a couple weeks ago. It's like the mechanical adjustment is off, but it's not, the throttle body is closed.

Any help welcome. I may just take the darn throttle body apart again.

 

[BTO]

The first thing to check is to make sure the throttle is closing completely. Remove the intake and give the throttle plate a visual. Then check for a vacuum leak.

 

[J-money$$$]

this happened to mine, and i noticed i could make the idle right forcing the valve shut. The butterfly valve was slightly warped and would not close tight

 

[Jon]

The butterfly is closing all the way and not damaged at all. So I started tapping on the sensors. The bottom sensor, I believe it's the Idle Air Control was gummed up. I bumped it with the hammer handle and idle dropped to 900 from 1500RPM. So I removed the throttle body again. Took the IAC off and cleaned the $hit out of it again. With the sensor removed from the little valve the valve is very easy to move from full closed to full open. With the sensor installed, the magnets keep the valve open about 1/8 open. Normal?

I'd like a more in depth idea on how the IAC actually works. My take is that the IAC is opened and closed depending on coolant temp. But is it opened by the actual heat like a carb choke and then that is monitored by the sensor? Or is it actually opened and closed by the sensor?

I'll let you know if it worked here in a few min. Had to do the 15min ECM reset to kill the CEL I got from unplugging the MAF with it running.

 

[J-money$$$]

The butterfly is closing all the way and not damaged at all.

thats what i thought too. manually rev your engine from the tb and smash that thing shut and hold it there. If nothing changes your right. Im telling you that less than 1/32" of movement cause my idle to change from 1500 back down to 700

 

[Jon]

The throttle body IS 100% closed. So at idle the only air supply must come through the IAC, right? At start up it idles at 1500 and after a minute it drops to 1000. Putting it in gear drops idle to 700. I guess it's better than 1500 all the time.

Lets just say that the IAC is good and working properly. Where does it get it's commands from, ECM? Why would it want to idle so high? Coolant temp sensor?

 

[J-money$$$]

okay, maybe your not have a similar issue. I know i had to push as hard as i could on it to get it to idle right. It looked closed but apparently was not. Well there is the ICA and the TPS and thats it for sensors i believe. you issue sounds like a vac leak.

any chance you recently cleaned your tb?

 

[Jon]

I just took the entire tb apart and cleaned it. I'm pretty sure this is going to be an issue with the ECM. Everything is working fine, no skipping so I don't think there's a vac leak. I looked a d listened around and can't find a leak and all the lines are in good condition. Id like to hook it up to scanner to get the details on the ECM.

 

[J-money$$$]

i was asking about the cleaning because this similar issue didnt start until i cleaned my tb. then all of a sudden idle issues started

 

[theizzardking]

Lol People commonly knock crap into the iac when cleaning the tb, the iac is on the bottom of the tb , easy for stuff to fall down into the iac and clog it up , look around for the right up , I mean after all how common is an ecu failure ? Plus cleaning the iac is another free hopeful fix .

From the high idle sounds like it could def be in the realm of the iac


Lol sorry you've been there and done that , lol , maybe it's the actual iac

 

[Kmvreter]

If it's the ECU it will throw a code so I doubt it's that.
Possible intake manifold gasket leak? Had this on a previous ride. Put the intake shorkel back together. With the engine idling, spray WD40 around near the base of the intake manifold, including the back of the engine. If the idle spikes higher then that means it's sucking in the spray as extra fuel. Simple check and worth a shot.

 

[Jon]

Hope not, but I'll give it a try.

 

[turbofreak]

Remove the throttle body from the engine. Yes there are two coolant lines going to the t body but you can use pinch off pliers to keep coolant from spilling. Clean out IAC passage/t body again and cycle the throttle body open/closed several times manually. Let it slam closed.

I had the same problem with my 4runner after cleaning the T body, high idle or no return to idle and this procedure was recommended to me by a Toyota Master Tech. It worked for me, hope this helps.

 

[quicksilvr]

The butterfly is closing all the way and not damaged at all. So I started tapping on the sensors. The bottom sensor, I believe it's the Idle Air Control was gummed up. I bumped it with the hammer handle and idle dropped to 900 from 1500RPM. So I removed the throttle body again. Took the IAC off and cleaned the $hit out of it again. With the sensor removed from the little valve the valve is very easy to move from full closed to full open. With the sensor installed, the magnets keep the valve open about 1/8 open. Normal?

I'd like a more in depth idea on how the IAC actually works. My take is that the IAC is opened and closed depending on coolant temp. But is it opened by the actual heat like a carb choke and then that is monitored by the sensor? Or is it actually opened and closed by the sensor?

I'll let you know if it worked here in a few min. Had to do the 15min ECM reset to kill the CEL I got from unplugging the MAF with it running.

I just had an IAC all apart on my friends new '99 to clean and test it, since he was getting P0505.

Here is what I learned: it takes a LOT of carb cleaner and q-tips to actually get the whole thing clean. Make sure you blast cleaner into the pivot end too (around the part that the magnet goes over) After you have the entire thing really clean on the inside from using q-tips and a toothbrush, spray WD-40 into the whole thing and work it in by opening and closing it manually.

To test: reassembly the IAC, and using a scrap piece of wire, attach one lead to the (+) on your 12v battery, and one lead to the (-). Apply the (+) lead to the center pin. Apply the (-) lead to either of the side pins. Depending on which one you pick, it will either close or open. Apply the (-) to the other side pin, and it will do the opposite of what it just did.

It should close 99% of the way, and open 100% of the way. When sitting at rest, it's open about 10-15%.



Beyond doing that, Just make sure your coolant passages are clean, the hoses are good, and your little vacuum line is hooked up.