Tachi

Greetings!

Backstory:
-1996 Honda Accord, likely originally an auto (I'm at least the third person to own it after the swap)
-H22A swap, likely a Euro-R
-OBD-1 conversion harness with a chipped/converted P06, ostensibly running Crome
-Euro-R manifold, H22A IACV relocated to firewall
-IACV and relocation plate clean enough to eat off of
-IACV is not locked-up, it will affect the idle

I've observed a faint, rpm-independent hum in the vehicle. Key on engine off no hum, key-on engine running, hum, let the engine stall and leaving key on, the hum is still there. After removing the stereo from the list of potential problems I listened around the engine bay after stalling it out and discovered that unplugging the IACV silences the hum. I'm disinclined to believe the IACV is bad because it will work, though right now it will surge after coming to a stop, the fluctuation getting progressively worse until it almost stalls out, then goes back to 800 rpm and firmly stays there until the engine is put under load again. The surging most likely is the air, but what is causing the hum?

(EDIT) Right, so I checked and there is no air in the coolant line to the IACV, though there remains no coolant in the loop under the TB.
-I unplugged the IACV while the engine was running. As expected, it stalled. Plugged back in, restart the car, CEL, but running. However, lightly applying throttle, at 1700rpm it drops and begins surging, bouncing between 1500 and 1700 until enough throttle is given that it jumps up to 4k+. I go back under the hood, unplug the IACV and manually fast-idle the engine, and it still does the bouncing between 1500 and 1700rpm with light throttle application. I pull the ECU fuse, plug it back in, car starts and runs normally.

So this tells me that the IACV is not actually performing any idle management. Could it be the IACV was bad to begin with and the idle/tuning was set around the bad IACV?

Also, might not be related, lots of vibration in the car. Possibly a skipped tooth on one of the cams on the timing belt but the tensioner is still in good shape, the belt isn't flapping about when I rev it with the timing cover dislodged. Replacing a half torn front engine mount did nothing for the vibrations. Engine appears to rock side to side rather than fore-aft.

hoopty hopper

i notice it says it has the h22a swap id look more into the proper mounts for the swap for side to side vibration and removing the side mounts for inspection vs leaving them mounted and trying to inspect them and does the steering wheel oscillate back and forth while driving?what trans is mated to that motor? side to side vibration could also fall into steering and suspension, wheels and tires

for your idle issues its hard for anyone to figure out without knowing what all was changed when tuning was done.(stoichiometrics)

I would try throwing a stock p13 in to start with to workout any wiring/sensor issues...
1500-1700 is pretty high idle when 650-850 is more average i'd try looking for vacuum leaks using a can of carb cleaner or starter fluid(not for the bbq) spraying down the whole intake manifold and see if there is a leak and tracing down all vac lines making sure theyre all properly connected, check the fitv also.
Check throttle body blade see if its stuck open /disconnect cables attached to throttle body see if it lowers if not try pinching the throttle body to the closed position with your hand to see if it effects the idle.
check reference/signal voltage and continuity on tps, map, iacv, egr, iat, and ect look for irregularities your reference voltage should be 5v
start with these and happy hunting

Tachi

Hon, this post is from over a year ago.

-The vibration turned out to be an out of balance fleabay clutch kit from the previous owner.
-The idle issues were because it was tuned poorly on Crome. A Hondata tune solved all of my drivability issues.

hoopty hopper

crazy it showed up as new post lol talking to myselfs