AllthumbsM

Facts, live in the mid-west (think KC area). My 2001 ES-300 doesn't start one morning in December - is towed to a reputable local mechanic (per someone's recommendation). 3 weeks later, he and his colleagues replace the 02 sensor and the IAC. They get the car running, in general it runs and shifts fine. HOWEVER, ever since he replaced the IAC (and upper bank 02 sensor). It idles high. Meaning, every-time, I turn the car on, the idle shoots up to 2250 RPM and does not adjust (whether the car is warmed up or not). When I place the car under load (i.e., in gear) the idle immediately drops to 1100. Note, the car is old (I realize that) and I don't care that in a perfect world I should get 24 mpg/when I now only get around 19.5/mpg.

Fast forward, in late April I take the car back to Mechanic #1 and please ask him to find out why the idle has always run high. He has it for a week, tried replacing the IAC (or at least so he says) same result/ says it might be the computer going out on the car. Gives me back the car (but doesn't charge me).

Month later the P0128 code shows up. Thinking that the thermostat needs to be replaced, I take the car to a different mechanic (i.,e. #2) to a) fix that problem, b) see if replacing the thermostat will fix the high idle, c) and if not, diagnosing why the idle is high. Mechanic #2 does replace the thermostat, code is removed, car still runs great EXCEPT for the high idle. Note, again, that the car has always run great since it was repaired in late December.

Mechanic #2 says on the invoice: "check throttle plate and it was dirty, cleaned the throttle plate and relearned the position of the throttle body, and performed diagnostic and found intake tubes were busted and the IAC was not functioning. Customer needs to take the car back to where the IAC was put on. Installed new air intake hoses."

Please answer me the following questions, as I am pretty livid about what Mechanic #2 did (or didn't do):
1) if #2 removed the thermostat (did he have easy access to remove the IAC that was on my car. Meaning, #2 could he have called and told me what a functioning IAC would have cost instead of telling me to take it back to #1.(which I wouldn't do - as #1 never could find out why the Idle was high)
2) is there a sure fire way that a layman can determine if the IAC is functioning? If so, how?
3) is it possible the #1 is right, the IAC is not broken, but the car's computer is not working regarding the IAC? (If so, can the computer be tested? ....just to find out what's really malfunctioning or broken?)
4) can auto mechanics return parts for credit from the parts store? I ask this, because I don't know what benefit there was in what #2 did regarding the high idle problem. Let's say he confirms there is a high idle, which we all knew to begin with. When the thermostat is replaced, it didn't correct the idle issue. Now for the crescendo, when re replaced the air intake hoses THAT didn't correct the idle issue (so what's the point of keeping them installed!!!!!) BTW, #2 charged me a reasonable hrly rate of $110/but 3 times what the retail costs of the installed parts were. Seriously!!! Each air intake hose was $85!!

Please give me your thoughts AND tell me if there is there any way I (or a buddy who has brains) can test the current IAC without taking everything apart. Note, if it is the car's computer going bad, I can live with that, it just seems to me that two purportedly reputable mechanics should be able to find out what is causing the idle problem - regardless of whether it's cost effective for me to have the problem fixed..

[Last, but not, least, and apologies in advance for being repetitive: the car runs great!!!! ...but for the idle issue)

Arsenii

Hello,

Do you still have an original IAC Valve?
What brand of IAC valve did you get, is it genuine Toyota, Denso or something aftermarket?

High idle usually doesn't cause the MPG to drop that badly, at least if you are not sitting in traffic jams all day long. Check the Engine Live Data, look for Calculated Engine Load, as well as MAF and Temperature Sensor readouts. If on idle you have high engine load and low MAF readings, your issue can be caused by a vacuum leak somewhere. The best way to check for one is to do a smoke test, but for now, try starting the engine and blocking the intake passage, the engine should die pretty quickly, if not, there is likely a vacuum leak that causes the engine to continue running, then you will have to listen carefully for any hissing sounds around the engine.

IAC valves, as far as I am aware, are quite durable on those cars, all that usually happens to them is that they get gunked up over time, but they are pretty easy to clean out, here is a thread about it. Did the first mechanic ever tell you what prompted him to replace that valve in the first place? Did he returned an old part to you?

The way IAC works on that car is pretty simple, here you can find a detailed description. In short, there are two coils that once powered, turn the rotor one way or another, opening or closing the valve. To check it, all you need to do is make sure that both coils are intact and have roughly the same resistance, then check that you can spin the rotor itself. With that, if the valve that is currently in your car is not original, I can't be certain it would ever behave normally.

Before taking stuff apart though, try disconnecting the pigtail coming to the IAC valve, see if that will help in any way. The valve has a fail-safe function, there is a bi-metallic spring that, as the engine warms up, tries to straighten up, gradually closing up the rotor, thereby dropping the idle. The car won't run perfect, but if if the idle would start behaving closer to what it should be, there may be a chance that ECU is either not controlling the valve, or sends some erratic input to it.

I think the reason the #2 mechanic told you to go to the one who did the repair is so that you will have at least some chance of proving that it was a mistake made by the first mechanic, making it much easier to ask for a refund for a job not done. It may be counter-intuitive, but in this specific case, the second mechanic may have saved you a lot of headache and fighting with the first mechanic, while taking liability concerns off his hat as well. At least that would be my best guess.

Did you get the old parts back?
What parts and coolant did they use for this repair, genuine or aftermarket?
By Air Intake Hoses, do you refer to the Part Numbers listed: 17881-20100, 17882-20130?

It's been a while since the last time I went to a repair shop, so I may be off in my judgements, maybe someone else could chime in with a better explanation. $85 is a LOT for each hose, even by OEM standards, you most definitely overpaid for those. The problem is that it appears to be a normal practice in the industry to mark up the prices for parts, there are no laws strictly prohibiting that, which is quite shady.. If you got the old parts back, check if they were in need of a replacement to begin with, which may add another leverage point. Conflicts like that is something no one wants to be a part of, so it may be possible for you to come in and really ask for a return, considering the amount you overpaid and the fact that nothing changed, it should be a lot easier to come up with a compromise.

Other thing to pay attention to, thermostat and coolant are things you really want to have OEM from the dealership, using aftermarket can cause a lot more troubles than in would resolve, while not being that much cheaper, so make sure to check that as well.

Hope this helps and best of luck!