I think those things would cause the CEL to come on with an error code about the EGR system.
(but I don't want to discourage you from checking anything that might be crudded up or stuck)

 

Yeah, that's I figured as well.

Plan is to pull the plenum with the throttle body & clean it, replace the gasket & maybe the throttle body gasket for good measure.

Looks like the only real fun part is pulling the rear coolant hose from the IACV. Boy that was a crappy job for someone with big fat hands. Took several days for the 1000-tiny cuts to heal.

Bonus ignition switch job as that is cutting out & driving my son insane...and it's not eligible for the recall (probably done already by the PO). Going to be a fun Saturday.

 

I don't think so. If it were open all the time you might get something similar, but the idle would be low. If it was "cycling" off sequence you might get something similar, but still low idle. If it was closed or not enough lift, it would idle low and kick a code. Plus, with either 1 , you'd get a CEL light on, and a code kick on.
Since you have a high idle, it's more than likely a vac leak.

 

I hear you. I wish they would have pushed that wall back 2 more inches, so you could get your hand back there.
While you have the plenum top off, pull the EGR valve off and clean the passage between the EGR and the plenum. It won't hurt anything to do so, and most people wait until the EGR kicks a code to do the job (split the plenum and remove the valve to clean the port), or in other words tear back into it again just to clean that port. Just something to think about.

 

Good idea. Thanks.

In addition to the plenum & TB gaskets/cleaning, will be replacing the plugs, wires, rotor, cap, and doing a valve adjustment. I'm betting the valves have never been done & that they're all tighter than hell.

Aaaannnd my son now reports the oil light flickering on at low/dropped idle. With 180K on it, I see an oil pump replacement in my future.

Boy, do I miss externally-mounted oil pumps.

At least, I'll now know how old the timing belt will be, since I'm not missing a chance to change it. May try bumping up oil weight &/or using a 'miracle' oil product until I heal from this job & psychically prepare for that one...although I hear the VTEC ain't gonne like it.

And the eight-month-old cheap-*** D/S power window assembly has, um, soiled the sheets. Going with the more 'spensive one. Have a harness for the passenger door, which has always been non-functional.

Otherr that that, the car is perfect! :V

 

OK: I'm completely stumped.

The plug I was pulling was not the IACV plug; it was for some sensor on the throttle body itself (between the firewall & the TB). Which is especially stupid, because I, myself, replaced the IACV a few months ago, and you think I'd remember that it's on the back side of the plenum. Not to mention I was staring at it while cleaning the plenum.

ANYWAY

This morning, I removed the throttle body & plenum. They were incredibly filthy. Would post pictures but my phone died. Cleaned them up completely & reinstalled them with new gaskets + aviation cement. Car was a bitch to start because of all the crap I washed into the intake manifold, but an enormous cloud & five minutes of wild idle gyrations later, it settled down into about the same idle it had before. Verified everything was plugged in & piped, warmed it up, pulled the (wrong) plug, and (of course) nothing changed.

After a bit of searching around (and considering an Alzheimer's diagnosis) I finally remembered where the IACV was, and pulled the plug on that.

The idle went *UP* about 800-RPM, and I heard a sucking noise. Plugged it back in; sucking noise went away, idle came back down. Lather, rinse, repeat.

Any ideas about what the hell is going on?

 

The IACV might be learning.

 

OK, we're (my son & I) are beavering away on it. Stay tuned for a Sunday update!

 

It's kind of rare, but it could also be a bad ECU. I've read that on another forum, where the user couldn't get the idle speed to come down and level out. He replaced the ECU (had it programed to match his key too), and all is well. It doesn't happen that often, but it does happen.

 

Things appear to be settling down. Son reports the car ran fine today on a mix of local & highway driving.

If anything pops, you'll be sure to know. Otherwise, thank you all for your time and expertise; they are greatly appreciated!