revs drop below idle when clutching in

I have a factory B16A3 in a 1995 del sol. The problem is that when i am
driving, and press the clutch in, the revs drop like a normal car
would, but mine drop further *below* the idle, then go back up to idle.
it hasn't stalled yet but at it's lowest point idles very low 100-200.
and its really annoying because you can never tell if it'll stall.

i just wanted to see if anyone else has this prob.

it never happens when the engine is cold. It's problematic when the
engine's lukewarm.
And seems to do it less after its reached FULL operating temp.
it is the WORST if I drive the car, park for 1 hour, then go drive
again. then it gets really bad.

Suggestions of where to start looking?

Thank you.

 

clean the throttle body

 

thanks for the suggestion mista bone.
today when i replaced the fuel filter, i removed the intake arm for
easier access. I then had a chance to look at the throttle body
butterfly (plate) and inside the intake manifold. using a paper towel
wrapped around a screwdriver i wiped the black oily residue off the
walls.

i'm not 100% sure of course, but i wouldn't call it excessive. it
seemed like there was a fair bit of build up. i will test drive again
after we finish dinner.

should i just remove the throttle body or the whole intake manifold to
solve this 100%?

thanks

 

I forgot, but I should also mention that my car bogs down at low RPM.
1-5k rpm. once it was so bad, that in 2nd gear i was at WOT and the car
wasn't speeding up, barely maintaining constant speed. cars were
honking from behind. : (

I'm sure this engine performance must be related to my idle problem.
here is a list of repairs/tuneups I have done:

OEM NGK Platinum spark plugs
OEM fuel filter
K&N Air Filter cleaned and resprayed with K&N filtercharger kit
Valve Adjustment
Replaced OEM Cat with Carsound high flow cat

**OEM PCV valve (just ordered will come monday - not installed yet)

From the research I have done all this could possibly be from a vacuum
/ emissions problem. but i certainly don't know a lot about that stuff.
where to begin?? pcv? egr?? evap?? iac? so many possibilities for a
n00b such as myself. makes my head spin. where to begin? just steer me
in the right direction, that's all i ask. I'll do the research and
solve the problem.

thanks!

 

when my 98 civic cx's O2 sensor went out, one symptom was the engine
sputtering and dying when i clutched in to coast to a stop.

 

hmmmm, interesting...Good thought on the O2 sensor. I'm not getting any
codes at all though. but you gave me an idea!

what if i have an exhaust leak right before the cat, and the outside
air is throwing off my O2 sensor?? That means the ECM must be supplying
a crazy AF mixture, hence i'm bogging?

when i look under the car at where the exhaust manifold meets the cat,
i see a little space between the two. i don't see any fumes since the
weather is so hot. perhaps i blew the gasket? i do autocross and my
manifold is the bottleneck on my otherwise skunk2 catback. i will
definately take a closer look at this when i jack it up to do my oil
change.

i'm willing to take any other advice/suggestions! thank you!

 

Have you ever had the valves adjusted? First Generation CRV's show
similar symptoms just before they start burning valves . . :-(

'Curly'