If the IACV is operating somewhere in range, but not at it's "sweet spot", you might not get a CEL. But you might notice some funny behavior. Like for example a more difficult situation like you're driving at 2,000 rpm, foot off the gas because you're engine-braking. Suddenly you press down the clutch pedal, and the engine maybe stalls instead of running smoothly down to a 750 idle.

 

Jim,

Just tried the routine. Does not appear to be working. When unplugged IACV, radio off, blowers off, the engine started revving up and down oscillating at about 1000-1300 RPM. No screw adjustment could change that by going all the way in and out. Any idea? Hope, I am not going to hear, I need to replace the TB.....

Thanks

 

If it's surging with the IACV unplugged, you might need to look for vacuum leaks.

Not sure about air in the cooling system, because the way that works is it messes with the FITV - and your car doesn't have a FITV. But you could still do your best to remove air from the cooling system.

Is the throttle plate clean? Does it close all the way (just not quite wedging stuck closed)?

 

Not sure about throttle plate. When I replaced IACV, I pulled out the air intake and pocked inside, the plate did not look spotless, so I wiped the exterior out a little, but it felt like it was springing back ok. I am assuming, venting the cooling would be taken care of by flush and feel? I am sensing, may be I should get professional involved at this stage.

 

Air tends to hang out in the thermostat housing, so there's a bleed screw there. It looks kinda like the bleed screws on each of your brake calipers. Unscrew it a bit until the air comes out & you get nice liquid stream.

 

Would you do it on running engine or turned off? Not exactly sure where to look for it, but I can probably pull out my Haynes and figure that out. And if that was causing the problem, I should be able to see steady RPMS and regained adjustability on the screw when the IACV is unplugged, correct?

 

First look for (& fix) vacuum leaks. I'm not sure about air in cooling system causing this, but I'll say it's another thing you should check.

I haven't had my car do just what yours is doing, so I'm hoping other people will chime in with ideas. The idea that you can turn that screw all the way in yet the engine still idles high, says that the engine is getting air from SOMEWHERE.

 

Just an update. Had vaccum checked and idle reset using the old cleaned IACV. No leaks of any kind found. The idle could not be set using the "direct replacement" IACV. All went well.

Lesson Learned: Do not buy the "direct replacement" parts for Honda, especially the ones that are electrical and have anything to do with your car performance or ECU monitored. The OEM parts might be more expensive, but will save you lots of time and money in the long run in terms of rework, agravation, and additional repairs.

 

I let my 2001 Accord sit for months when traveling to China. When I came back the idle went bad. I took it out on the freeway and gunned it to 90 MPH a few times and the idle settled. That told me my throttle body was dirty, after cleaning it, no problems.