Please help, IAC issue...

[jermag24]

Update: I bought a used IAC (Idle Air Control valve) off Ebay, It is very clean, and passes the resistance check in the maintenance manual. I also hooked 12v up to the correct terminals, and the IAC valve opens and closes great. But, when I everything and start the engine, SAME PROBLEM! Idle jumps to 2k upon start up and stays there. I get a check engine light after 5-10 seconds. When I unplug the connector, the RPM goes down to 800-900, and the engine acts normal. So,

1) Checked that everything is hooked up correctly, and it is.

2) IAC valve passes resistance check, and acts correctly when voltage applied.

3) Double checked TPS, non-issue. Positive it has to do with the IAC. Especially because when I unplug the IAC, the RPM drops to normal idle speed.

4) This all started when I took the IAC off to clean it, because the idle was a little rough when it was hot out, and the A/C was turned on. Here's my original post if it helps. PLEASE give me some ideas/past experiences.

7-12-08:

I was cleaning the throttle body/Idle Air Control valve on my wife's 98 Camry to correct a fluctuating idle. Hooked the IAC up to 12 volts to help with cleaning, put it all together and got a check engine light. Idle won't go below 1200 RPM. When I partially block the IAC port in the throttle body with my finger, the idle goes down.

I checked the continuity before all of this, and the IAC's resistance was about 25 ohms on both neg. terminals (within spec). Now when I check it, I get 27 ohms to one terminal, and 2 ohms to the other.

1) Did I fry the IAC valve by maybe crossing the pos. and neg. leads?

I've pulled off the valve since then, and it opens and closes with voltage. But the CEL stays on, and the higher idle may be a safety concern.

2) I found these IAC valves at autopartsplace.com for $185, anyone know of a cheaper alternative? I'd love to find a used one I can clean and install. Thanks for your help!!

[1996camry]

call around junkyard in your area to see they have IAC for your model? that would be the cheapest round..

[jermag24]

I'll try that tomorrow. Really, I just need the half that has the connector on it. I'll have to do some testing today and see if it's easier to drive as is, or with the IAC unplugged. Just until I find another one.

[samarai912]

when you say it high idled 1200 was that a cold start? have you tried to disconnect the battery for 2 minutes to reset the ecu?

[jermag24]

Originally Posted by samarai912

when you say it high idled 1200 was that a cold start? have you tried to disconnect the battery for 2 minutes to reset the ecu?

1200 was with it warm. I've been resetting the ECU every step of the way. I have the IAC unplugged now and it runs fine. It just idles a little slow when it's cold, and normally when it warms up. It's also a little abrupt when you let off the throttle, but it's only temporary until I find a used IAC to install. Thanks, if anyone here has a used IAC, I'd be happy to buy it!

[Kep]

What is the CEL code? You may have bumped something else inadvertantly. A lot of auto parts stores (Auto Zone around here) will read the codes for you. But don't necessarily rely on their analysis of the code. Post the code here also and get some alternatives.

Kep

[jermag24]

CEL=Check Engine Light.

The resistance of the idle control valve is way out of spec (per chiltons manual), so I'm sure it's that. Hopefully I can find one in a salvage yard.

[jermag24]

Bump for update added. Please help if you can.

[jermag24]

Bump for any troubleshooters out there. Any Toyota techs??

[jermag24]

Well, after installing another IAC, same problem. I took it to get the check engine light codes read, and got: P0505: Idle Control System Malfunction.

Probable causes:
IAC stuck closed or open (new IAC functions great, so no).
Open or short in IAC valve circuit. (again, tested good).
Open or short in A/C switch circuit. (A/C works great)
Air intake duct or hose loose (Just reinstalled, and double checked, so no).
PCM malfunction. (Sounds like the most probable cause). Any way to check it?

Question: My wife's camry is a '98 I4, NON California emissions. If I buy a PCM (ECU) off Ebay, do I have to make sure it's for a Non-California model? Any thing else to think of when buying? Thanks!

[Kep]

The air conditioner has an idle up mechanism. I suspect that it is why they suggest that you check the AC.

It would be much safer if the replacement PCM/ECU has an identical label if you want to be sure that it is compatible.

You mentioned that you might have crossed the IAC wiring so possibly you did damage the PCM. It used to be possible to open up the ECU cases (1990). I'm not sure if you can open a 1998's or not. If you can, look inside for a singed area on the motherboard. That would be a good indication of a malfunction.

Is there any chance that you have an acquaintance with the same model that would let you run your wife's PCM in their camry? If yours is bad their Camry will run poorly too. If yours runs good in their Camry then it is something else. Putting a bad PCM in a good car is prefered to putting a good PCM in a suspect car. If your Camry damaged your PCM you wouldn't want your Camry to damage someone else's PCM by installing it in your Camry.

The next cheapest thing would be to get a used one from a salvage yard or eBay. It is highly unlikely that you would just happen to buy one with the same problem (if any, Camry ECUs have had a very good reputation and seldom fail). If you experienced the same problem then it would be the car. If the IAC problem went away then it would be the original PCM. A new PCM will likely cost several hundred dollars.

I'm not real suspicious of the air intake since unplugging the IAC changes the symptom. However, squeeze it to demonstrate any cracks rather than just look at it.

Luck,
Kep