I have a 95 GS-R which is having a problem with idle when cold. When you first start it up it idles at about 2500 with dips down to normal~800. This is rough to drive as it is a sudden drop and yanks the motor mounts all over. When it is warm, it runs fine. I have replaced the stupid IAB valve on the back side of the intake, to no avail.
Any suggestions??

 

iacv you mean?

 

Rite;
NE1?

 

My d16 did that also. I alwasy thought it was the IACV sensor. Did you replace it with a new one? Maybe its still faulty. Otherwise just wait a couple minutes till it warms up before you drive..like your supposed to.

 

this seems to work like 50% of the time,

purchase some carb/intake cleaner (The Honda top engine cleaner is the best out there part#08732-900 and spary/pour on the inside of the IACV, leave it over night and rinse it off w/ some carb cleaner, put it on the intake and see if it works. sometimes inside the valve it gets sticky w/ over excessive garnish buildup (very common w/ cheap aftermarket filters).

if it doesn't, buy a new one.

also, stick your finger inside the T/B port when you have the intake tube off and see if it idle normal, thats sign the vavle its sticky.

hope it works

 

if this is a swapped motor it could be wiring issues if you replaced the iacv with a new one

 

When i had this problem with one of my dseries motors the problem was a faulty thermo valve on the backside of the TB, you might want to check that.

 

on the back of the iacv, there should be a plate with two screws. take the screws and plate off and expose a single screw. tighten the screw all the way down. my buddy's GSR did the same thing, and thats how i fixed his.

 

Got the right idea. Fast Idle Thermo Valve, located on the bottom of the throttle body. Replace it. The cheap fix is quoted above. IAC controls idle solo once the motor has warmed up. Cold idle is controlled by the FITV.

 

same thing with mine was fixed right away.
just get a flathead and turn right!
replace plate and screws, And call it a day