2003 Accord Throttle Surging Problem/P0505

My 2003 Accord is experiencing a throttle surge problem similar to what I have read about in this ng. 6 cyl. No other apparent problems. 120K on plugs. 27mpg.
It warms up OK. Then it begins surging between 1000rpms to 2000rpms. Up and down continuously surging. It happens when it's sitting still or when being driven. Cruise on or off doesn't make a difference. Using an Actron code reader I get a "pending" P0505 (Idle Control System Malfunction) which seems reasonable. I don't know where to start to address this problem. Any advice would be greatly appreciated.
Penthor
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penthor snipped-for-privacy@yahoo.com wrote:

===================== (since you're supposed to check this part anyhow) The first (cheapest) place to start is your cooling system. Just make sure there's coolant up to the underside of the rad cap and the reservoir should be filled up to the MAX mark. Once the engine is warm it preheats the throttle body (and several computer sensors) with hot coolant so it can screw up your idle if there's AIR in the system.
Honda premix is a safe one.
'Curly'
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Coolant level is full.
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penthor snipped-for-privacy@yahoo.com wrote:

Hi, ICS is basically a variable resistor. Poor connection, dirt build up is known for causing trouble. You can check it's operation with a multimeter manually moving it if you undertand what mean.
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I checked all the connections I could find. They were pretty clean. I'm not sure what you mean about checking the "ICS" with a multimeter. Do you mean one of the sensors? Which one and exactly how would I check it?
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In article
penthor snipped-for-privacy@yahoo.com wrote:

Idle air control valve?
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That's where I am now. I read on another site that the IAC valve controls the idle before the engine warms up, and the MAP sensor controls the idle before the engine warms up. I tried to remove the IAC valve to clean it as I read elsewhere. The 2 screws are very soft metal and I'm afraid of stripping them out. So I'm planning on removing the throttle body to better access them.
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On Apr 5, 5:58 pm, penthor snipped-for-privacy@yahoo.com wrote:

Actually, the MAP sensor controls idle after warm up.
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penthor snipped-for-privacy@yahoo.com wrote:

no it doesn't - that source is wrong. the iacv controls idle - idle air control. the map sensor is part of the input the computer uses to compute idle values, but it doesn't control the idle system in any other way.
if you're getting the iacv code, you need to test it per the honda manual. helminc.com.
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penthor snipped-for-privacy@yahoo.com wrote:

the iacv is a honking great water heated valve mechanism built into the air intake, not the throttle body. and it's held on with bolts, not soft metal screws.
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JB, Thanks for the info on sensor function. May be that the other source is incorrect. However, the IAC valve on my 2003 6cyl Accord is attached to the bottom of the throttle body by screws, which are easily stripped. I can personally vouch for that info. You are correct about the water heated characteristic. That is one of the checks when idle problems arise; is the coolant level OK. Thanks for replying.
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On Apr 6, 2:37 pm, penthor snipped-for-privacy@yahoo.com wrote:

Problem solved. I cleaned the TB and IACV and reassembled, and it ran fine, better than ever. While I had it off I tested the IACV with 12v and it worked fine. On the road again:)
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JB, Thanks for the info on sensor function. May be that the other source is incorrect. However, the IAC valve on my 2003 6cyl Accord is attached to the bottom of the throttle body by screws, which are easily stripped. I can personally vouch for that info. You are correct about the water heated characteristic. That is one of the checks when idle problems arise; is the coolant level OK. Thanks for replying.
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