96 Civic Idle

I've got an oscilating idle on our recently purchased 96 Civic Ex AT (112k
mi) with a new throttle body done just before we got it. Here's a synopsis
(warm engine): If I rev to 3000 rpm and let off the pedal, the idle drops
dramatically to 1000, then up to about 1400 then back down. Repeat the
1000-1400 oscillation a couple times, then finally to rest at a reasonable
(but maybe high) 1000 rpm.

Cold idle is about 1500 rpm; I hate engaging the AT at that engine speed.

Any ideas? I haven't got the service manual yet. Was there an adjustment
missed when the throttle body was installed?

Thanks a bunch.

Scott

 

After removing, cleaning and reinstalling the TB on my '94 Civic I had
very similar symptoms. Turned out there was a little fragment of old
gasket left between the TB and the intake manifold. The resulting vacuum
leak caused the fluctuating idle.

To find it, I filled a squirt bottle with rubbing alcohol and sprayed
around the various parts of the intake system with the engine running
(most people suggest using carb cleaner, but rubbing alcohol is all I
had at hand). When the spray hits the location of the vacuum leak you
will notice a dramatic drop in engine RPM.

 

Clean the Fast Idle Thermo Valve.

I'll bet the car is a DX right?

--
Charles Tague
93 Honda Civic DX HB
1.6L SOHC VTEC 14.85 @ 89 mph,1.98 60 ft.
With ZEX 85 hp ZEX 13.09 @ 103 mph, 1.81 60ft.
86 Pontiac Trans Am
225/50/15 GForce Drag Radials
305 peanut cammed 15.29 @ 88 mph
http://home.cinci.rr.com/mistab0ne/

 

Nope, EX. Is that valve specific to the DX/LX configuration?