crazy fluctuating idle - apexi pfc djetro, everythings legit

[alesserfate]

heres the deal

after my car warms up the idle starts revving between 500 and 1500 rpm going up and down whenever i come to a stop at a light, its pretty fucking annoying

car: s13 sr20det, apexi metal hg/arpstuds, sard 850s, greddy im, gt30, apexi power fc djetro, has a good tune makes 411whp

sometimes after a little driving it stops doing that, and when it does taht if i blip the throttle as its about to drop and get it dead on, it will stop and idle normally

what i've checked:
-vacum leak tested everything from the intake filter, no leaks
-checked grounds on the IACV, it's fine
-tried changing the idle on the pfc, no effect
-IACV gaskets are fine

also, this exact setup was in my old car before and it was fine, the only things iv'e changed are the engine wiring harness, and i've had it retuned for a little more power

on another note, until the car warms up completely, if i touch the throttle as its doing its crazy fluctuation, on its way 'revving down' down, i can smash the pedal all i want until 100% and there will be no response at all until it goes back into its upwards cycle towards 1500

once i start driving, until its completely warmed up, every time i shift gears (hence letting off the gas when upshifting) the moment i step on the gas again there is 0 response, once again, even if i floor it, for a few seconds, and then all of the sudden it comes alive

I have an AEM wideband, and as its revving down, it leans out all the way, then it riches out, then leans out again

I was thinking it could be my TPS ?

any other tips ?

i can't come up with anything else to check.

[ddf2006]

check your mass air flow sensor

[alesserfate]

check your mass air flow sensor

djetro = map sensor

[inyowindow]

you vacuum tested everything from the intake filter. did you check your intercooler piping for leaks, or possibly a vacuum hose that has a cut/leak? also, do you have a bov? and is it hooked up correctly?

[alesserfate]

you vacuum tested everything from the intake filter. did you check your intercooler piping for leaks, or possibly a vacuum hose that has a cut/leak? also, do you have a bov? and is it hooked up correctly?

yes i have

there is no leaks anywhere, we went over that many times that has been ruled out

yes there is a bov, and yes it is hooked up properly and functions

the car drives perfectly fine, i daily drive it, but the crazy idle is getting really annoying.

[rc1honda]

Well you might have to do the idle learn procedure again. You will need data-loggit or something like it so you can save your tune and load back into the PFC after you do the idle learn procedure.

What you would have to do is initialize the PFC meaning you WILL LOSE ALL SAVED TUNES! So thats why you need a dataloggit to reload your tune.

First you initialize the pfc. Then you input your injector corrections. Next, turn the PFC boost controller to off if you are not using it.

Start the car and let just idle for 10 minutes. After the first 10 minutes turn the deforster on to simulate load and let it idle for another 10 minutes.
Then turn the AC on if you have if not just turn your headlights on and let it idle for another 10 minutes.

So all in all you should have let it idle for 30 minutes. After 30 mintues if your idle is still hunting play with the idle screw on the IACV untill it stabilizes.

Then load your tune from the dataloggit and bingo.

[jspaeth]

heres the deal

after my car warms up the idle starts revving between 500 and 1500 rpm going up and down whenever i come to a stop at a light, its pretty fucking annoying

car: s13 sr20det, apexi metal hg/arpstuds, sard 850s, greddy im, gt30, apexi power fc djetro, has a good tune makes 411whp

sometimes after a little driving it stops doing that, and when it does taht if i blip the throttle as its about to drop and get it dead on, it will stop and idle normally

what i've checked:
-vacum leak tested everything from the intake filter, no leaks
-checked grounds on the IACV, it's fine
-tried changing the idle on the pfc, no effect
-IACV gaskets are fine

also, this exact setup was in my old car before and it was fine, the only things iv'e changed are the engine wiring harness, and i've had it retuned for a little more power

on another note, until the car warms up completely, if i touch the throttle as its doing its crazy fluctuation, on its way 'revving down' down, i can smash the pedal all i want until 100% and there will be no response at all until it goes back into its upwards cycle towards 1500

once i start driving, until its completely warmed up, every time i shift gears (hence letting off the gas when upshifting) the moment i step on the gas again there is 0 response, once again, even if i floor it, for a few seconds, and then all of the sudden it comes alive

I have an AEM wideband, and as its revving down, it leans out all the way, then it riches out, then leans out again

I was thinking it could be my TPS ?

any other tips ?

i can't come up with anything else to check.


I wanted to let you know that i have this issue IDENTICAL, to a TEE, to how you described it.

It started when I put the big cams in and Greddy Intake Manifold and has never gotten better.

I believe there are multiple causes.

Old/shitty IACV....

Also, the self-learn was presumably learned before the big cams. The IACV idle response settings may not be good for the new cams.

The results is these oscillations. My car does the EXACT same thing.

When the car is colder, it usually results in it dying.

When it is warmer, sometimes it oscillates, until it steadies itself or until I catch the throttle on the way down.

I really think there is not much you can do about it.

I think opening the throttle plate a little bit using the adjustment screw would help the issue, but it also makes it nearly impossible to have an idle below 1100-1200 RPM.

Right now, my idle is about at 850-900 RPM with timing at idle usually around 15 degrees or so (I have Idle Ignition Feedback turned on to help prevent fluctuating idle).

Anyway, like I said, this is a common issue for big cams on this car....other people on the PFC Datalogit forums have the same issues.


I also have the same issue as you, where when the car is cold, it doesn't really respond to throttle instantaneously.....it drops first and THEN revs up....


Never have figured that out, and have just learned to accept it.

[steve shadows]

You may just need to have some support with your correction map settings and the lower regions of the map.

[jspaeth]

You may just need to have some support with your correction map settings and the lower regions of the map.

Without your foot on the gas, with the car idling, and the car warmed up (hood up so IAT sensor doesn't heat up), the only things that should be affecting this are:

1) IACV condition
2) PFC "self-learn" settings that it knows
3) Fuel in those cells
4) Timing in those cells
5) Whether or not you have idle-ignition feedback turned on
6) How open the throttle plate is
7) Physical parts that are on the car and making sure they are installed correctly


This really isn't rocket science in my opinion.....there are known "reasonable" amounts of timing to use at idle and you can easily use a wideband once you get it stop fluctuating to nail down fuel.


I think I could richen it up a bit to "stabilize" the idle a bit, but honestly, I don't care enough and don't want AFRs greater than 14.7 at idle (I run them in the low 15s or so).


Odds are it is the IACV and perhaps weak ignition.....


If the RPMs drop down below 500, it is tough for your alternator to put out much voltage and the spark suffers badly.


With a shitty IACV that has the wrong "self-learn" settings in there, it is easy to imagine that it always overshoots (allows TOO MUCH air in) when the idle dips below the target....and then process repeats itself.



Anyway, I am not super concerned.

[alesserfate]

good to know that im not alone in this, you guys got more things dead on as well

-yes my car has hks cams (256 or 264 i don't remember anymore)

-the IACV is a fresh one and worked great on the motor it came from (fresh sr from a front clip, and I cleaned it out good before installing it onto the greddy intake manifold

-i have splitfire module and coilpacks for ignition

so now looking at the solutions that some of you suggested

- I don't have fc datalogit nor know how to use it, so i would not be able to back up my tune and relearn the idle

- I have not changed anything in my engine bay since doing the relearn, cams and everything etc were already installed as it wouldn't make sense to tune my car without the cams and then install them

- the only thing I can think of is that there were no headlights on my car when it was being tuned, so we used the blower motor to simulate the electrical load

I have come to accept the way it idles and what not and drive it around, but it just gets on my nerves sometimes. Anyway, don't know what to do next whether to leave it or..

[jspaeth]

good to know that im not alone in this, you guys got more things dead on as well

-yes my car has hks cams (256 or 264 i don't remember anymore)

-the IACV is a fresh one and worked great on the motor it came from (fresh sr from a front clip, and I cleaned it out good before installing it onto the greddy intake manifold

-i have splitfire module and coilpacks for ignition

so now looking at the solutions that some of you suggested

- I don't have fc datalogit nor know how to use it, so i would not be able to back up my tune and relearn the idle

- I have not changed anything in my engine bay since doing the relearn, cams and everything etc were already installed as it wouldn't make sense to tune my car without the cams and then install them

- the only thing I can think of is that there were no headlights on my car when it was being tuned, so we used the blower motor to simulate the electrical load

I have come to accept the way it idles and what not and drive it around, but it just gets on my nerves sometimes. Anyway, don't know what to do next whether to leave it or..


From all of the stuff that I have read, the best way to "stabilize" the idle with big-ish cams like this is:

1) Richer mixture, like maybe even 13.5 or something
2) Higher idle to get a more stable, less pulsating flow (maybe as high as 1100 RPM)
3) More timing than you would usually see at idle (maybe in the mid 20's or something).


Mine doesn't ALWAYS do it.....once it is stable, it won't start bouncing around.

It is usually only when the car is cold or when I slow down quickly from higher revs.

[alesserfate]

hmm thanks for your advice, appreciate it