Testing IAC valve - Toyota Nation Forum : Toyota Car and Truck Forums

duke_togo · 02-01-2008, 09:00 PM

I couldn't start my Camry today, well, it would start, but the idle would immediately drop and the engine would die. I read a few threads:

http://www.toyotanation.com/forum/t150678.html
http://www.toyotanation.com/forum/t142922.html
http://www.toyotanation.com/forum/t77262.html

... and decided it was probably the IAC valve. I had been having a rough idle problem on and off in the past year, ran some seafoam through the brake booster line and it helped a lot for about four months.

Anyways, my question is about testing the IAC valve. I have it out, cleaned it up a bit, lots of carbon deposit. I'm following the guide at http://www.**********s.com/camry/. On page eg2-274 it says to hook up leads to a battery and test that the valve opens and closes.

Do they mean to hook it up to the car battery?? Just wanted to make sure before I fry something.

Thanks all.

Also, expert speculation as to other possible causes of this problem are welcome.

***Eye8Pussies*** · 02-01-2008, 09:11 PM

yup, to a 12v source

dc_98_cam · 02-01-2008, 09:15 PM

The IAC test on p. 274 looks fairly straightforward .... For convenience, you might have to buy or make some test lengths of a reasonable length... Try hardware store for clips .. just put a little solder on one stripped end for a probe tip ... Don't see how you could damage anything ...If you look closely, you can probably see which terminals are being referred to in the test diagram... Don't think any damageable electronics are involved here. However, to avoid accidental sparks and other damage to your car ... You will want to be sure to disconnect the negative battery cable from the car battery prior to performing the IAC test.
Definitely a good idea to clean the IAC of all fouling, rust, or whatever ... and inspect moving parts for smooth operation.... Not sure what the recommended lubricant is... might not be anything at all.
Let us know if there is any improvement.

... Just curious, have you taken your EGR valve and tubes apart ... this is frequently a carbon fouling situation... though not sure it is related to start up rough idle.

duke_togo · 02-01-2008, 09:16 PM

Thanks for the quick reply! Well, I hooked up and nothing opened up. Looks like it is stuck in the closed position.

Guess I need to get a new part tomorrow morning. Thanks again.

duke_togo · 02-01-2008, 09:22 PM

dc_98_cam, I haven't taken a look at the EGR valves and pipes yet. I just now printed it out some stuff to try (since I have everything off already).

On the IAC valve, I didn't really see any moving parts, other than that cylinder (or whatever) that I guess is supposed to move if it was working. No idea about lubrication, the factory manual didn't say anything but check resistance (passed) and open/close operation (didn't pass, assuming I did it right).

I actually stopped by the electronics store and bought some clamps for easily getting on the battery terminal posts and it had some probe tips with alligator clip extensions. I couldn't get the voltage to carry well on the tips, so I used the alligator clips.

I also took the whole battery out. On the bright side, my battery tests out at 12.80 V. :-)

dc_98_cam · 02-01-2008, 11:56 PM

I was thinking that you should see some sort of mechanical movement ... such as the port vanes .... something obvious....if the IAC was actually working correctly....
...At least this is what the manual test procedure implies.
... If it showed some reasonable resistance value, then the coil is probably good, and would indicate that it is just mechanically frozen... due to carbon or rust. Maybe try some sort of rust penetrant spray or solvent... going into the mechanical section...
I used to use a product that I bought from GM dealers ... called Heat Valve Rust Penetrant Spray ... or something like that ... for difficult rust situations.... It cost $12 or 15 though.
One possibility is to get a used IAC from a salvage yard ...Not sure what a new one would cost ... probably a lot.

duke_togo · 02-02-2008, 09:16 AM

Yup, just called around this morning to the dealership and a few auto part places. I'm looking at about $200 for a new IAC valve. So the thought is definitely crossing my mind to go pull a part from a salvage yard, but I may just bite the bullet get a new part.

Regarding the rust penetrant spray, do you mean something like WD40 or PB Blaster because I've got those. Guess it's worth a shot.

dc_98_cam · 02-02-2008, 10:50 AM

Quote:

Originally Posted by duke_togo

Yup, just called around this morning to the dealership and a few auto part places. I'm looking at about $200 for a new IAC valve. So the thought is definitely crossing my mind to go pull a part from a salvage yard, but I may just bite the bullet get a new part.

Regarding the rust penetrant spray, do you mean something like WD40 or PB Blaster because I've got those. Guess it's worth a shot.

I've tried Wd40, PB blaster, and several others, but prefer the GM product.
It seems to have a little more reactivity .... Sometimes, you will have to let it soak in for awhile, and maybe repeat the application a few times, but will usually make a difference.
Do you think there is a possibility that the moving part within the IAC has come loose from its drive shaft ... the thing that rotates it? If that is the case, then, any amount of penetrant spray won't fix it. You will have to get another one someplace.

DFBonnett · 02-02-2008, 11:02 AM

Quote:

Originally Posted by duke_togo

Regarding the rust penetrant spray, do you mean something like WD40 or PB Blaster because I've got those. Guess it's worth a shot.

On our '93 V6 I just pulled the IAC back from the TB, hosed it out with spray carb cleaner, let it soak a bit, hosed it again then, blew it out with compressed air. That was a couple of years ago and no recurrence of the problem so far.

FWIW
YMMV

duke_togo · 02-03-2008, 09:44 AM

Here's an update, fellas.

I soaked what I thought were the right areas with PB blaster for a short period of time and tried to test it again. I'll probably continue to muck around with this old part to see if I can get it to work, but I needed a working car, so I went ahead and bought a new part.

After hooking it up to the battery, the valve flies open and close when you touch the leads to RSC, B, and RSO. Now that I understand what it's supposed to look like, I can see that the old part was stuck pretty good.

Anyways, everything came back together pretty quickly and the car cranks up and idles beautifully now. Before I would be happy if it idled at start right at 1000 rpm, but now it shoots up and idles near 2000 rpm. I need to read the manual and figure out if this is right, seems slightly high, but it's better than below 300 rpm and dying so I'll take it for now.

Thanks all for the advice and support. Any other thoughts or suggestions are welcome.

dc_98_cam · 02-03-2008, 12:39 PM

Quote:

Originally Posted by duke_togo

Here's an update, fellas.

Anyways, everything came back together pretty quickly and the car cranks up and idles beautifully now. Before I would be happy if it idled at start right at 1000 rpm, but now it shoots up and idles near 2000 rpm. I need to read the manual and figure out if this is right, seems slightly high, but it's better than below 300 rpm and dying so I'll take it for now.

Thanks all for the advice and support. Any other thoughts or suggestions are welcome.

Just a thought .... was thinking that the ECU might possibly have a memory record of the sensor conditions when the IAC was jammed, and be giving a signal command to inject excessive fuel at startup ... So you might try resetting the ECU .... disconnect battery for a few minutes I guess ... and see if there is a difference in the startup RPM. ... Just guessing here ... not certain that the ECU works in this manner.

95CamryV6GTA · 02-03-2008, 06:31 PM

Hi.

Last week i had rough idle after a long trip more than 1 hour.

So after reading this thread and others, i cleaned my throttle body and let the liquid soak into the IAC.

Today after the same scenario, it refused to idle, but it run's perfect once you control the throttle

So i'm guessing that the IAC is the culprit?

Was removing the IAC easy ?

Thanx

DFBonnett · 02-03-2008, 08:03 PM

Try disconnecting the neg terminal on the battery for a minute. That will allow the comp to reset to default and may solve the idle problem.

95CamryV6GTA · 02-03-2008, 08:09 PM

Yesterday, whilst i was cleaning the TB, i had started the engine.

As such the MAF would have gone crazy and the Check Engine light came on. So i has to reset the ECU by removing the battery .

duke_togo · 02-09-2008, 05:59 PM

Quote:

Originally Posted by 95CamryV6GTA

Was removing the IAC easy ?

I wouldn't ask my mother to do it, but as long as you have a basic set of tools (sockets, wrenches, pliers, etc.) and can follow directions (the factory manual was great, the Haynes manual, not so good), it was pretty straightforward.

(1) Don't forget to drain your coolant. I only drained the block.
(2) The screws holding the IAC valve to the throttle body were kind of a pain. Two came out ok, two got stripped out. I used PB blaster + vise grips to get them out, and I was ready with a screw extractor in case that didn't work.

Good luck.