2003 Accord Throttle Surging Problem/P0505

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(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'

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.

Idle air control valve?

Coolant level is full.

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?

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.

Actually, the MAP sensor controls idle after warm up.

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.

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.

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.

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.

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:)