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

 

======================

(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