Sticky Idle? Rb25det

[MickEdge]

Yeah basically as the title has described.

Revs up

Decreases, Sometimes holds at 1100rpm momentarily and drops back to normal idle

Other times drops back to normal idle no worries

Such a weird little sticky point Any ideas? Anyone seen this before?.

Video for more clarification. Cheers

[zoomzoom]

A consult cable and diagnostic program would show you whether it correlated with changes in the AAC valve duty. Maybe the AAC just needs a clean?

[MickEdge]

I have the stock plms data cable + datascan. A while ago it threw fault code 17 tcs/acs/slip. Dont know if that had anything to do with it though. I cleared the ecu. Turned the car on and off and that fault code had never shown up again and the idle remained sticky.

tonnes of people keep directing me to clean the idle air control valve so i guess that is the goes.

any further help is appreciated though

[Ben C34]

Do the basic stuff first.

Clean the IAC as told.

Then if that doesn't work its time for a thread with videos etc. Not now.

[89CAL]

Why does the tacho needle flicker a bit?

Is it really an issue?

It looks to me like its just a decel fuel cut issue, like sometimes the decel fuel cut is deactivating at different times or something. I found a similar thing happen when pulling up to a set of lights (not sure if it was on the Power FC or stock ECU). It would idle a bit higher until the car speed decreased to zero then went back to normal idle

[ErOR]

I have exactly the same issue. When stopping revs will sit at 1000 or so rpms and then drop to normal, it's way worse when cold.

I've cleaned aac, checked ignition bits, looked for leaks many times and I have no idea where to go next. Could the aac valve be slow or something and need replacing? I have a small missfire on idle too which is possibly connected.

25de

[MickEdge]

Do the basic stuff first.

Clean the IAC as told.

Then if that doesn't work its time for a thread with videos etc. Not now.

Well the thread seem to net a bit more info and help me out a bit, Looks like others have come forward with some constructive criticism also. I understand you dont want forum flood all the time. But hey. It might help someone

Why does the tacho needle flicker a bit?

Is it really an issue?

It looks to me like its just a decel fuel cut issue, like sometimes the decel fuel cut is deactivating at different times or something. I found a similar thing happen when pulling up to a set of lights (not sure if it was on the Power FC or stock ECU). It would idle a bit higher until the car speed decreased to zero then went back to normal idle

It'd have to be an issue. Its annoying as f**k pulling up at the lights and having your rpm tacho do all weird shit and the car rev funnily when all youve done is press the clutch in and come to a stop.. and its climbed up to 1100 and back down to 850 for no reason.

Well it gets to me severely anyway. Also its alot worse on cold. Cold reversing out of my chicane like driveway clutching in and out has the revs sticking and dropping alot

I have exactly the same issue. When stopping revs will sit at 1000 or so rpms and then drop to normal, it's way worse when cold.

I've cleaned aac, checked ignition bits, looked for leaks many times and I have no idea where to go next. Could the aac valve be slow or something and need replacing? I have a small missfire on idle too which is possibly connected.

25de

Ive been busy with work but im cleaning my iacv and a couple other checks this weekend ill let you know what happens for me

yes yes yes yes so much worse on cold..

Points more towards the iacv.

I appreciate all the brainstorming.

Im yet to feel a misfire in mine though. illl keep you posted

[MickEdge]

After watching the video again and seeing it rev up and back down to idle so cleanly and easy. Thats natural rb heartbeat.

Seems to be some whacky tachycardhia somewhere to be sorted

[89CAL]

It doesnt really seem like a dirty AAC because it doesnt do it all the time (but anything is possible)

Is it just a standard ECU or has it got an aftermarket or piggyback unit fitted?

Is there anything that might be causing the problem that you arent realising, for example clutch in, in neutral and so on?

Is your throttle cable too tight? Or is something holding it ever so slightly off being fully closed?

Trying to think of an electronic reason, but it really has to be the ECU telling the AAC to hold the car at 1100rpm momentarily

Will keep having a think about this one

[MickEdge]

It doesnt really seem like a dirty AAC because it doesnt do it all the time (but anything is possible)

Is it just a standard ECU or has it got an aftermarket or piggyback unit fitted?

Is there anything that might be causing the problem that you arent realising, for example clutch in, in neutral and so on?

Is your throttle cable too tight? Or is something holding it ever so slightly off being fully closed?

Trying to think of an electronic reason, but it really has to be the ECU telling the AAC to hold the car at 1100rpm momentarily

Will keep having a think about this one

This weekend when i clean the aac will be the first teller for me and that will cross some stuff off the list for us both

Standard ECU, no piggybacks of any sort on the car

If the throttle cable was too tight itd be a permanent thing in my mind. Cable tension cant waft in and out like a saggy ballsack

Everything about the throttle body seems perfect to me.

It has to be an electrical issue between the ECU and the AAC haha. Fingers crossed anyway lol. Time will tell

[89CAL]

Just trying to rule out some more basic stuff first. I've seen crazier things before.

If its stock ECU, after you clean the AAC etc, do a reset on the ECU. It might sort itself out

[sonicz]

I can gurantee you its not the throttle cable sticking or anything mechanical like that. That's the Typical ECU Trim/adjust computer stuff it does.

Something is causing your RPMs to stay a bit higher than what is expected, then the ECU goes oh shit thats too high for this amount of idle throttle it and dips it. Happens to my R33 as well. Here are some possible things you can look into that haven't been mentioned yet that have made my skyline exhibit these symptoms.

1 .AAC Valve Screw - Maybe the screw on the AAC vavle is a bit to high. Turn it clockwise maybe 1/4 of a rotation, so about 90 degrees, and see if that has any impact. IF not try do another 90 degrees to a full 180 and see how that has affected it. I wouldn't go past a full 360 turn if its not fixing the issue. Remember your stock position.

2 .High fuel pressure and any fuel pump wiring changes - Check your fuel pressure. When I changed my fuel pump and did a fuel pump rewire my idle RPMs were higher than they were before this until the ECU auto adjusted. but I noticed when stopping at lights the RPM would hold 1300ish just like yours before the ECU autocorrected. It seemed the car wanted to lurch and stay in higher RPMs instead of mellowing out. It would drop to 800ish and you had to just breathe on the thorrtle and it would rise to 1300 again, then dip, etc. Had to adjust AAC valve.

3. Something like Air condition running, power steering pump asking for juice, light, amp, a electrical drain on the alternator etc causing the ECU to want to raise the revs.

4. Timing not set properly, too high - Having the timing too high can cause this issue as well. Is your CAS adjusted about in the middle? See a lot of R34s with the CAS fully advanced.

Thats all I can think of right now

Edited April 16, 2015 by sonicz

[scotty nm35]

4. Timing not set properly, too high - Having the timing too high can cause this issue as well. Is your CAS adjusted about in the middle? See a lot of R34s with the CAS fully advanced.

^^ This is a common one I see.