high idle while coasting

[hoang]

hey guys, i dunno if the car is supposed to do this but i just noticed it recently, when im driving about 60kmph and i put it into neutral, the rpm stays put at 2 thousand and drops down to about 1.5 and back to 2 thousand again, my rpm then finally drops to about 700-800 when im almost completely stopped. any input whether this is normal or not? thanks

car is 89 s13 coupe with a 91 KA

[Def]

You should have a fast idle while moving... about 1.1-1.3k RPM on a stock engine. The surging idle sounds like you might have a vacuum leak or something like that.

[astrophixvox]

i agree sounds like a vac. leak somewhere.

[tgd89]

My 90 SOHC does the exact same thing, I have pretty much every vac line pluged. My car is cammed so that is why mine is so high, but for a stock car as said, 2k is kinda up there.

[wiggafly808]

Try cleaning your throttle body, MAF, and IACV.

[sultan]

when i put the clutch in on my coupe it stays at 2k until i come to a stop, then drops to normal idle. kinda weird but i never cared to find out why (93 coupe with auto ecu, s14 KA, trans from a sohc).

[DohcKA]

mines kinda surges too but it idles at 800 sometimes.... basically when its warm it surges but its not consistent... it idles at 800 a lot still.... mines idle at about 1.5rpm then surges up then drops down to 800.... most likely its the iacv... they go bad a lot

[hoang]

how do you guys suggest cleaning the throttle body, IACV, MAF. i went out and bought a can of throttle body cleaner. for the throttle body, just take off the intake pipe and giv'er? i cant seem to find the IACV, its supposed to be the back of the intake runners but i dunno what it looks like, anyone have a picture? also for the MAF, it seems as though the 2 philips screws are stripped to i cant turn them, any suggestions?