What would cause my RPM to all of a sudden go up and down,

at idle it goes up from 800 to 1200 then down, constantly.

chance IAC, same thing.

engine is b18c "pr3 pistons" ITR Cams , Skunk2 IM, P&P, DC 4-1 headers AEM cam gears,in 90 gs using pr3 with vafc.

using stock b18a injectors.

i tried adjusting the vafc and brought down the pressure to -38 its a bit better but still flucuating.

Engine is running smooth but does'nt seem very powerfull .

should i get my pr3 chipped or the vafc is enough.

no ecu codes.

Anyone with a similar setup. can you please tell me your VAFC setting so i can try to solve my problem.

All help is appreciated.

GsTeg90


Modified by GsTeg90 at 3:51 AM 4/23/2003

 

have you checked or replaced the idle control valve ? i could be faulty. i had a similar problem on a b16

a lot of jdm motors get banged up pretty bad during shippinf, particualrly the intake manifold. my idle control valve was broken, my rpm would jump from 800 to 2k or so when idle. , its an easy replacement, i believe all b-series ICV's are interchangeable, I used one from my old LS manifold.

just something simple you can try to see if that is the problem.

 

My motor was completly rebuild. all sensors have been replaced..

i'm getting code 2, its 2nd o2 sensor. i'm at work now.. but someone told me to check my coolant, that can cause this problem.

if it was coolant, why would i get code 2?

GsTeg90

 

ttt

GsTeg90

 

Would be interesting to see what people say. I have a B17 swap in my 93 and when using the stock P61 ecu, I get a very slight fluctuation at idle. Say from 800 to 900rpms. When using the chipped P28 (Mugen program) I get a large fluctuation. From 1,000rpms to 1,500rpms. Whats odd is that the Mugen chip makes it worse and increases the stock idle to 1,000rpms. I have cleaned and replaced my IACV just as you have, still no luck. Only difference is I am getting no codes..

 

swaped the IAC, codes are gone.. but idle is still screwed. when cold jumps like from 2500 to 3500, when warmed up, jumps from 800 to 1200.

tried adjusting with vafc and no luck.

need help!!!!!!!!


GsTeg90

 

any vacuum leaks?

 

nope , no vaccum leaks. driving the car is perfect. hits vtec and evrything... but it revs like crazy on idle.


GsTeg90

 

my original post has been updated.

still need help

GsTeg90

 

I have the same problem with my idle. It is really pissing me off. When I start the car it idles around 2k to 2.5k. It drops to about 1500 but then start revving up and down on it's own up to like 2k or 2.5k rpm. I also changed my iac and still have the same problem.

What could it be??? I am also not getting any codes @ all. I also have a mugen programed ecu for modified motor.

 

Bump

GsTeg90

 

http://www.hondaswap.com/~pills/idlefix.html

i wrote a little article for hondaswap detailing my shitty idle experiences.. it sounds like i had all the problems you guys did...

does your FPR have a vacuum reference??

 

no fpr installed.

checked and no vaccum leak either.

i should also mention engine was completly rebuilt and it has less then 1800kms. this problem did'nt happen right away,, it happened after i changed oil. @1200kms.

 

ttt

 

is it possible that somehow my o2 is unpluged and if so, would it cause this problem

GsTeg90

 

I'm betting you have air in your cooling system. My old teg use be like that until I bled the cooling system of air. worst case senniro bad or defective head gasket. all the symptons points to the air bubbles in the cooling system. why replace a IACV when you're not even sure when you could've troubleshooted it cheaper.

 

yeah check your coolent, you might have to bleed it.

 

motor is brand new new, just finished rebuilding evrything.. so all gaskets should be fine.

GsTeg90

 

Take a Flat head with you and adjust the idle.

 

tried that did nothing... it jumps almost 1000rpm when its cold. when it warms up it jumps from liek 700 to 1200 evrytime it idles

GsTeg90

 

My car still did it when I swapped my chipped p28 for a stock p72. It did a little differently but still did it.

 

Fast Idle Valve under the throttle body, it was lose all the way, tightend it and put it back, and now the car is back to normal.

Thank you all for you help.

 

That is the piece under the tb that the coolant runs thru right.? I bypassed mine ran the hose directly to the IAC.