Tachi

...aside from a retune. 1996 Accord, JDM H22A, likely a Euro-R, or a Type-S w/ Skunk2 intake manifold, bought in that configuration. Car is tuned on Crome via a chipped P06. I am the third owner since the swap, none of it was done by me.

The idle is rough, in that there is alot of vibration in the car. The IACV, when tapped w/ screwdriver handle buzzes. Loudly. The valve has to be unplugged, and replugged, or the engine shut off and restarted to get rid of the buzzing. The engine sometimes hunts, from 700rpm, up to 1200, then back down, as low as 200 rpm, before going back up. With the alternator unloaded (fuel and ignition only) it resolves quickly, but with the lights/anything else added to that load, the surging drops low enough that the engine shudders, almost stalling, after a few cycles the engine does stall. When driving and approaching a stop, when clutching-in and just coasting, the idle falls down to 300rpm before coming back-up to 700. With the alternator loaded, this sometimes results in a stall.

-No vacuum leaks that can be found with the carb cleaner that I can see.
-Brake booster check valve works fine
-PCV isn't the issue either. Tried plugging both hoses, did not change idle.
-Aftermarket TB w/o FITV, bypassed entirely.
-EGR blocked off, distribution manifold cleaned and blocked off with tan fiber gasket.
-Valves adjusted, most of the intake valves were too tight, a few too loose, but the engine is just quieter now, the adjustment didn't really change the idle.
-IACV is relocated. Adapter plate on the firewall and the valve itself clean enough to eat from, figuratively speaking.

Having eliminated the common problems, my working theory is that the IACV is performing sluggishly and not responding fast enough to the idle needs. I tried an IACV from the junkyard, which needed a good soaking in carb cleaner first, performed similarly, if not slightly worse.

I'm just looking for input before I spend the money on a new IACV.


(Edit 6/13/2015) I replaced the TPS with a Doorman unit and adjusted it (.49 closed, 4.52 WOT)(The TPS that was on there was going to fall apart if I tried adjusting). After bolting the TB back on and plugging everything back in, and letting the ECU reset, the car runs a little worse if anything, rough idle, occasional hunting, and throttle is still inconsistent and touchy. As well, now its propensity for stalling when coming to a stop is higher as well. (When RPMs are above 2000 and I clutch-in and let off the gas. Revs drop down to 300ish and don't want to come back up, often it does not recover and just stalls).

I am getting to my wits end here. There are no vacuum leaks unless my engine is somehow immune to the carb cleaner trick, valves adjusted, compression is even, timing is fine, TPS adjusted and within range. Yet the engine does not want to cooperate.

v4lu3s

I hate trying to get decent idle with Crome. Have you adjusted the advanced idle options?

Tachi

If I'm going to buy a license for Crome I might as well spend a bit more and pay Pure Tuning to convert it to Hondata. [Edit] I refuse to believe that a tuning shop would have let the car out the door idling like this.

I did just go out to check, and think I got the correct TPS voltage reading. .40v closed, 4.35v WOT. I just ordered a new TPS (current one is falling crumbling apart around the grommets, unsure it will go back down securely). This could also be the reason why its so gutless at light throttle.

Tachi

Replacing and adjusting the TPS did not work, see OP.

holmesnmanny

The iacv shouldn't make any noises at all. I would replace it.

Tachi

That's what I was thinking. Would a bad IACV also cause the sensation of a "hole" in the throttle map? That is, very little power from 0-30% and then a very abrupt jump in power from then on to WOT?

v4lu3s

No, but a bad tune can cause that.
After using both Hondata (s200 and s300) and Crome since they first offered pro/dealer licenses I have found that when Crome works it works well, and when it didn't work the most common problem was idle related. Without accessing the advanced idle options it was at times impossible to get a good idle, that's why my current car ended up with Hondata. I just got tired of messing with it. And if you think a shop won't push sub standard work out the door you have not been around cars long.

Tachi

The thing is, I yanked another IACV from an Accord in the junkyard and behavior was slightly worse as one would expect from a dirty junkyard IACV even after cleaning, but it also produced the low whining noise. I assumed its only audible because of its mounting to the firewall. I'm half tempted to try mounting it back to the intake manifold and getting rid of the couple feet of vacuum hose in case that's a contributing factor.

Tachi

Well, the new IACV doesn't make any noise. The car behaves EXACTLY the same as before. I bled the coolant again to make sure, I fruitlessly played with the timing, nothing.

Start the car, it idles evenly at 700 for several seconds, then drops down to a lumpier 500rpm and if you use the throttle, when releasing it it drops to 200ish and frequently stalls before it can recover.

There are no vacuum leaks that I can find. IACV relocation passages are clear. No CEL's.

Am I missing something? Please, if the answer is something dumb that I am at fault for not seeing please tell me to go back to google. I need something to go on. I am completely stumped at this.\