I'm with heysoundude far as going one step at a time. Takes more time, temptation is to just do all at once. But time constraints make us condense our process. If the plugs are easy to get to, I'd do them first, listen to idle quality/sound.
Putting the Groove deeper in the TB bore, can be touchy, but business card method works OK. I'd hesitate trying to go much deeper in TB bore than that.
I'd really like to see your pics of this baby!
Esp. the IAC arrangement.
BTW, I just went to ebay to get a look at this TB, I found this auction, pretty good price!
Well the link is too long or something, it won't copy in here. It's on ebay right now, it is 63 bucks w/ free ship. At first it looks as all plastic, then in more pics it looks metal...? anyhow now I see the layout if this is right one, the IAC air goes in at openings right under the throttle shaft, like an IAC re-route! It's DBW. Looks like as you say Ken the IAC air comes up thru a duct in the intake manifold and enters a small void in TB base, then the IAC channel splits and goes to each side of throttle shaft. Now I wonder 2 more things- is what we are calling an IAC channel/duct really an IAC, or is this something else, like EVAP/charcoal canister purge, or...? Does this TB hold the throttle plate fully closed or partly open w/ key off? I'm wondering if this is like the GM Vortec's where there is no IAC, and idle speed is regulated by where the ECM puts the throttle angle at. OR Is the plate normally fully closed, and idle RPM hot/cold whatever is done by air bypassing throttle plate via an IAC system?? Either way, Honda puts these openings in the TB bore in a good place out of the Groove's way. First one like this I've seen. No need to mess w/ these openings under throttle shaft IMHO. You could adjust How MUCH air goes to these openings w/ a bit of epoxy at the center point where the air comes in. If this Honda does control idle RPM via an IAC, and throttle is closed at all times when foot is off the gas- then find and mark the desired throttle angle in the bore and Groove there. Another clue would be if the un-cleaned TB has no dark stain under the plate, and if there's enough miles on it where the stain should be there, that says to me that the "natural idle position" of the plate is fully closed. OR if there is indeed a stain, and it's right at where the throttle is fully closed, that's confirmation that it uses an IAC to control idle speed. See why I'm saying all this?
If you've identified a throttle angle that seems ideal, could you have the TB in hand off the engine, connect the electrical plug, turn the key on--then using scantool or ultraguage readout for throttle angle position, position the throttle plate to the desired angle, then mark along plate edge in the bore w/ a sharpie pen? Then try business card, etc.between TB bore and plate opposite side from Groove to find what to use to get plate at the matching angle.
One thing Ron taught and I found out on DBW for the Chevy Vortec V-8's is to do just as you are saying re: putting the Groove a bit downstream in the TB bore from fully closed throttle plate, you need to avoid having the Groove at hot engine idle plate angle position. This is reason for the business card behind the plate when cutting Groove to get it downstream from hot idle position, else you can have excess idle speed. Ron further taught to check the TB for the dark stain in the bore that builds up and marks the normal hot idle position, this gives clear indication of where to cut the Groove, just a little further deep in the bore so to avoid the too-high idle RPM. Apologies, Ken if I'm repeating what you already know, but others may learn from seeing this. The big thing to remember is don't clean the TB bore if it's a DBW type, you want to see the black stain as a guide. Another thing to verify is how the plate moves to the hot idle position, when engine is off, the plate's rest position needs observed. W/ the Chevy Vortec's the plate rest pos. is partly open w/ engine and key off. At cold start ECM opens plate more for fast idle, and gradually closes to hot idle position as temps increase.
I've not Grooved any other TB's w/ DBW throttle control besides the Chevy 5.3 Vortec, so I'm curious to see if other makes behave as the Chevy does. and I'm now wondering if there was both a plastic and metal TB for this Honda, and if so why?
Last- A Gadgetman a few yrs. ago gave a tip for holding the Vortec throttle plate in position against the business card. Vortec TB's are spring-loaded and off position is slightly open throttle. He used modeling clay from a hobby store a big glob of it against backside of plate w/ the card between plate/bore. This frees up both hands, and good idea to hold TB in a small vice, now both hands are free to control the dremel flexshaft.
Ok an addendum to all this: I've looked at 4 pages of ebay auctions for this TB. All pics showed a metal body w/ black plastic housing over the drive motor. Most had an IAC valve integral to TB, with looks like an air supply hose to the IAC. A couple had no integral IAC. If yours has the integral IAC, could restrict air to it w/ a smaller dia. hose in the main IAC hose. Looked like the throttle plate sits just a small bit open at rest. And many auctions were under 100 bucks some under 50 if ya want a spare.
sorry for so long-winded, but all this figures into Groove-ing strategy for what the Honda TB I saw on ebay looks like.
You say this TB is plastic,, the ebay one I found is metal...??
Tracy G