IAC Valve Frustrations/Questions

Yes.

That may be true, but is an unlikely occurrence. The common failure mode for these is for the pintel valve to stick at minimum opening when the engine is warm.

Probably.

The IAC and O2 sensor are unrelated. Can't promise a solution for the O2 sensor, but do have one for the idle air control valve. My situation should be similar to yours. At 80,000 miles, the dealer had already replaced the IAC valve once, when rough idle on cold start returned. This is my own personal method, but seems to have worked fine for me. At the slightest hint of rough cold running, I spend three minutes, and then it seems to be fine for a long time. Long time readers of this group have seen this procedure repeated often. You'll need a 10 mm wrench and an aerosol spray bottle of Berryman B-12 Chemtool, generally less than $3. Remove the single clamp at the throttle body holding the large plastic air hose in place, and move it over to the right. Start the engine, cold, and allow it to idle. Spray a few short blasts of emissions control safe Berryman carburetor cleaner into the small rectangular hole at the bottom of the throttle body just right of center. This is the air intake for the idle air control valve. If necessary, keep the engine running by moving the throttle cable wheel on the left side of the throttle body. Actually, quite a bit of air rushes through the small air intake with the throttle closed at idle, so it doesn't take much cleaner spray to free the tiny pintel valve inside the IAC valve that controls air flow via a computer operated step motor.

Your O2 sensor, is a newer more sensitive version. For very reasonable cost, I would recommend using Redline complete fuel system cleaner. It has been approved by BMW for continuous use and can also help clean emissions components. No guarantee that your O2 sensor will live longer, but can only help, plus it will clean the intake valves and fuel injectors. A few dollars worth treats one hundred gallons of gasoline. Their web site has extensive technical data.

One poster reported that clean air gasoline formulations caused O2 sensor problems as you're describing, and that when the fuel formulation changed, his O2 sensors no longer required frequent replacement.

Not necessarily related to your situation, my Camry is a bit older than yours, and when replacing the oil pan gasket, the center exhaust pipe had to be removed. I could see the secondary O2 sensor at this point and it looked perfectly clean. The primary O2 sensor also tested very good at 120,000 miles. According to Toyota, a "lazy" O2 sensor can be caused by IIRC, being coated with contaminants, so there again the Redline can be helpful. It also contains a synthetic upper cylinder lubricant for protection and will likely increase usable power as well, due to cleaning all the injectors and gradually removing intake valve deposits.

If you perform your own IAC valve cleaning, rather than paying the $350, with your savings you can buy a lifetime supply of Redline fuel cleaner.

Thank you for your suggestions, I appreciate it. The Toyota dealer, by the way, "never" cleans IAC valves, only replaces them. Called another mechanic (not a dealer) to see if he was ripping me off, but he too says that he has stopped cleaning them because the procedure doesn't last...and it may do damage if I don't remove the throttle assembly to clean it. So...I'm stuck. One last question though, why is that all Camrys don't have this problem? In other words, is the fact that mine has this problem a predictor of future recurrences of it, regardless of replacing/cleaning?

I will definitely take your advice on the Redline fuel cleaner, thanks. Too bad an additive wouldn't keep the IAC clean, too...

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In the Days of Yore .... the hose carrying crankcase vapors from the valve cover to the air cleaner had ... a FILTER on it. Do you recall those coarse, fibrous pads in a little holder on carbureted American cars? SEEMS to me with a LITTLE ingenuity that a similar filter could be installed somehow. Yeah, you might say this is 'old school' but gummy IAC's are an old problem after the second screwing you get for a new part.

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- Philip @ Maximum Torque RPM

Setchell wrote:

"Setchell" wrote in message news:...

When the dealers clean the IAC assembly it is removed from the vehicle, so to reduce potential call backs and improve profit, one can understand why they always replace the part. Generally I agree with this philosophy. I always like to install new factory parts. At the major service interval I installed a new PCV valve and grommet, new gas cap, new PCV hose, new valve cover gasket, new cam, crank and oil pump seals, new plug wires, new distributor O-ring, etcetera. If it will improve operation, or reduce potential future problems, I'm all in favor of installing new parts, and since I perform my own labor, and often obtain discount parts pricing by shopping dealers online, the cost is quite reasonable. Two areas where this philosophy is altered is the the IAC valve, and the engine valve seals because even when these are replaced with new parts, the problem can recur. Toyota has such a brilliant design of the intake system and dual overhead camshaft multiple valve configuration, that I just consider cleaning the IAC valve an idiosyncrasy far offset by the legendary durability of the engine overall. I, too, had the experience of cleaned IAC valves sticking again before long. That's why I developed the method described for cleaning them, as a simple effective modification of the other cleaning methods I'd seen described. I believe you will be amazed at how simple, quick and effective your results will be, but it is best if you pick up the wrench yourself. You can use a 1/4" drive ratchet handle (from Sears) or a 10 mm "GearWrench" as I do, which is really slick. The idea is to be sensitive to applying only gently firm tightening to the hose clamp bolt. Chances are, you can learn to do this wearing good clothes, even keeping your hands clean, and completing the entire process in mere moments. The improvement in cold idle speed will be nearly instantaneous and quite long lasting. You need to have the engine running at idle, cold, for this procedure to be effective. I used to try spraying cleaner into the IAC air intake and turning the ignition switch on and off to mimic the method described elsewhere on the Internet, but those results did not last very long. When the engine is running, and air is flowing through the IAC valve, the cleaning is very effective. You've probably never used the Berryman product, but I've seen it work on other external engine areas, and also in separate cleaning for the throttle body which is done with the engine most definitely off, and it liquefies gum and varnish instantly and very effectively. I believe it is the precision of the pintel valve in the IAC that creates this condition. The computer controls very tiny movements. I've forgotten how many, but there are a number of "steps" or digitally sent instructions to move the tiny plunger inside the IAC, so it only takes a slight amount of oil mist being recycled through the intake to gum it up. The nice part, is that it only takes a tiny amount of spray cleaner to free it. You're just misting the aerosol Berryman a couple of times, and you'll see and hear the engine immediately respond. Afterwards, the cold idle speed will smoothly rise as it should. To recapture your affection for the Camry, consider that the aluminum intake manifold includes long individual runners that contribute an inertial supercharging effect at low to medium engine speeds, and if your version is like my four cylinder, there's a built in cold air intake system drawing outside air through the bumper fascia and up through the fender well, included in the stock configuration. The engine really is a marvel of design.

Called another mechanic

Here's where we part company. I don't like to have a mechanic touch my car. Through the years, I have found problems almost every time in checking the work later. I suspect that a mechanic "on the clock" even with their years of experience and special tools, does not take the time and TLC that an owner can with their own vehicle. This post is already long, but I could give numerous examples, some quite dangerous. Last time I changed the timing belt in connection with some other work, I found several errors which would never have been revealed ordinarily, such as the thermostat installed in the wrong position, chipped crankshaft pulley and stripped automatic transmission pan bolts.

Dealers do bench cleaning or replacement only. Our local dealer does clean the IAC valves, but it costs a lot more than $3. Perhaps you could shop on price if you need to have it replaced. Not a major job really, but it is a precision electromechanical part. Very common to replace them. Similar to the "dog bone" engine moving control rod, which are also commonly replaced, and if neglected can lead to increased wear on the other engine mounts. I suppose a "work around" could be to simply press the accelerator pedal a bit more when starting the car cold to raise the "revs". Usually you only have to do this for a short time. Maybe if you clean the IAC as I've suggested, the engine will fall apart, self destruct, and poke big holes in the crankcase leaving parts strewn along the highway. If so, I'm not responsible. But that has not been my experience. My car is maintained to perfection, I can run it up to redline through the gears (automatic), or cruise sedately down the boulevard, with the engine purring like a contented kitten, and it jumps to life instantly and smoothly on cold start. Works for me.

I think you'll be very pleased with the results. Just continue to use it over time.