2003 Honda Accord idle/computer problem

2003 HONDA ACCORD

69,000 MILES • 4 CYL • FWD • AUTOMATIC

PROBIE

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Being mechanically inclined, I changed the thermostat and changed the battery , since I hardly use the car.
But once I had it running, the idle speed fluctuates very noticebly. Thinking it was air in the system I filled the engine with 50/50 coolant/water through the upper
radiator hose but still the same. Never had this problem
before.
I'm worried I somehow damaged the computer because before I changed the battery I used one of those
manual chargers and therefore overcharged and overheated the battery. Or could it be the computer has to relearn its memory? I would get a new IACV if that's the problem but I doubt it's that because it ran perfect
before. Is there some way that the computer can relearn
without me taking it to shop?

May 31, 2010 at 8:28 PM

KHLOW2008

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41,814 POSTS

Hi probie,

Thank you for the donation.

When air is trapped in the cooling system, the IAC would not work correctly and it can result in the surging as described.

After replacement of the thermostat, you need to bleed the system which I believe you have not done so.

Remove the rdiator cap and top up the coolant if it is low in level. Run the engine with the radiator cap off and when the coolant level drops, top up the fluid. When coolant level stabilises, close the radiator cap and retest.

Actually there is a bleeder at the thermostat housing but since you have run the engine, it most likely is not required to use that to do the bleeding unless the coolant level is very low.

Jun 1, 2010 at 9:34 AM