Yes. IMHO, find a new dealer....but before you do have them order/sell you the o-ring : 16456-P8A-A01 and refuse to pay more than ~$2.50.

I wouldn't get into the "spring" part of the TB.....again just my opinion.

 

Thanks poorman212. The dealer gave me the "O"-ring for no charge.
I seen on You Tube where some guys disassemble the unit and also clean the spring assembly. Any reason why you don't think its a good idea?

 

A 1999 does not have a FITV. Beginning in 1998, the function of the FITV was built-into the new-style IACV (rotary valve). They're right, don't take apart the IACV.

But for Honda, it seems that failed IACVs are not too common. More often they are just dirty. Even more often yet, the whole idle-control system isn't set up properly.

 

Thanks Jim Blake for your help. Once again I have a 1999 Honda Accord EX V6, with 202,000 miles. Just finished cleaning the entire throttle valve and all the port holes, installed a new IAC, checked all hoses, clamps, checked coolant fluid, installed new air filter, but the engine is still idling up and down. When taken for a test drive, seems like plenty of power, acceleration and cruise control works OK. Came home and placed in neutral with the same problem with engine idle from 1,000 to 1,200 RPM. When I run the AC position the problem stops, but not in the heater control position. I'm stumped. Can you help? Thanks

 

Try again with the AC running. The AC compressor will engage & disengage according to its own compressor.

I wonder if the idle is flaky when AC "system" is switched on but during the times when the compressor clutch is disengaged.

I'm actually not sure where I'm going with this, except if it's the IACV itself that is failing it should have a flaky idle when the AC compressor is disengaged even when the AC system is switched on.

Are you sure you have ruled out any vacuum leaks anywhere?

Have you set the base idle (with IACV wire disconnected) down to 550 rpm?

edit: Wait, I guess that doesn't completely make sense, because you replaced the IACV. Did you get a new one or junkyard one?

 

Thanks Jim....yep bought a new IAC and I did find one vacuum leak. Had a code P0505. Checked all over and re-traced my steps and found one clamp missing off the breather tube to the air inlet where it connects just before the throttle valve. As soon as I installed that missing clamp, it seems to be working quite well. After the initial warm up, the RPM is running around 650. Just for curiosity sake, I disassembled the the old IAC control. It was extremely gummed up and I was able to clean part of it, but unfortunately, the cheap white metal casting has two bearings installed within the casing and impossible to remove along with the moveable vane. Its a complicated piece of equipment and has not been cleaned since 1999, I'm surprised it worked for that length of time. I was told by the dealer to clean it once a year because there charge is $210.62 plus labor for a new IAC. They DO NOT clean them. I also inspected and cleaned all the associated tubes to make sure none were blocked. After installing that missing clamp, I did take it for a test drive and it has plenty of power and pick up. Tried the AC and heater controls during the ride and also in PARK. All the heater and AC vents seems to be working OK, the two radiator fans come on as required and so far, all is well. I am going to try if from a cold start tomorrow morning because our temps will be going down to the low 40's in my area. Should be interesting if all systems are in working order. Thanks Jim for all your help. I am glad to have found this site and hope my input can help others. Thanks again.

 

Just to be complete...

After all of that, did you check the base idle at 550 rpm (IACV unplugged)? Then reset & allow the idle system to "re-learn" it's behavior?