Revs Bounce On Cold Start

[justin911]

hey ppls

for the last few months when my cars idling on a cold start it sits at like 600rpm.. if you start to drive or just touch the throttle it revs fine but then drops to about 300-400 then back to 600. after about 2 mins when the temp gauge has moved up about half a cm its fine and the revs sit on 750rpm or so and dont bounce around.

hmm come to think of it when the car is cold shouldnt it sit on like 1000-1200rpm or something higher like that ? anyways i had the bouncing idle problem (but when the car was warm, not cold) a while ago and i cleaned the aac valve and that fixed that up, but im not to sure what to try clean now.. ? I was searching and theres some cold start valve or something ?? where abouts is that ?? is that the same as the air regulator ?? i had a look in the workshop manual, i couldnt see it on my actual car though.. anyone got any pics or any other ideas what it might be ??

thanks

[MBS206]

Engine temp sensor working properly to the ECU?

[justin911]

i started the car just now to have a look. I drove about an hour ago so the car is still hot, but the needle is about 0.8cm above the bottom and the pfc rekons its about 63degrees. The middle which it always sits on after about 5 mins of driving is about 84..85 degrees so i think thats working fine like it always has.

but ya the idle is fine now cause the car is already warmed up a little bit..

[blind_elk]

Have you had the PFC programmed / tuned for "cold start"? Maybe it needs a bit more fuel or timing when it's cold.

BTW, I don't see anything in your initial post that mentions you have a PFC - such information would be most useful.

[series2r33]

I've got the same sorta problem, wheres acc valve, u said before...

"a while ago and i cleaned the aac valve and that fixed that up"?

I also have the pfc but even when my car warms up i still got the problem not really bouncing but drops low and sometimes stalls, but if i ease the clutch in its ok as apose to "stomping it in" when im rolling up to lights, driveways etc but the revs are sometimes ok and sometimes low...

[West]

If you have the PFC, just tell the TUNER to fine tune your cold start, they do go out of wack after a bit of time.

All your tuner need is for your car to stay there the night so he can start it cold the next morning.

[dezz]

Same justin. might doesnt have idling issues like yours, but it doesnt feel right when its cold....when driving that is...

Need to leave it overnight this time so they can sort out the cold start

[mad082]

it could be the iac valve. the aac valve is what always gets cleaned. the iac is down under the intake plenum. (i think thats why not many people clean it) from what i know of it, it controls the idle air for cold start.

[justin911]

ya i found the little barstard the other day.. looks impossible to get out though, all i can see is like 1 bolt

it could be the iac valve. the aac valve is what always gets cleaned. the iac is down under the intake plenum. (i think thats why not many people clean it) from what i know of it, it controls the idle air for cold start.

[Godzilla32]

it could be the iac valve. the aac valve is what always gets cleaned. the iac is down under the intake plenum. (i think thats why not many people clean it) from what i know of it, it controls the idle air for cold start.

Yeah does sound like AAC Valve, it bleeds more air into the secondary air system to bring up the revs when cold. Have to get it apart and clean it out. Also inspect the tension of the spring.

[blind_elk]

You can't (and don't need to) clean the IAC (Cold Start Air) valve. It is not operated by a servo-motor, as the AAC (Auxilliary Air Control) valve is. It is a simple bi-metallic strip, heated by electric current - as it warms up, it causes a plate to cover the air bleed hole.

If it has any sort of problem, it may be that it is not fully uncovering the hole when it cools.