Jump to content
SAU Community

Recommended Posts

RB25DE+T PFC idle

Hey guys,

Had this minor annoyance for a very long time, from memory probably since the powerfc was installed and tuned 6+ years ago. Maybe because I'm getting older it's starting to annoying me more.

I turn the car on in the morning and idle is high, 1500-1700rpm, but stable. On the hand controller it all looks pretty stable, not sure if idle this high when cold is normal with other powerfc's but so far it doesn't annoy me.

As I'm driving around and idling at lights while the car is still warming it's still sitting at 1500rpm, on the hand controller once the water temp gets to about 59-62 degrees it starts hunting, from 1500 rpm down to 900rpm and back and forth every 1-2 seconds and will continue like this until the water temp gets to about 72+ degrees then idle is perfect, 850-900rpm. The only way to control it during this time is let off the clutch a little bit until it bites and slowly lower the revs, then I slowly press my foot down on the clutch again. If I put my foot down too quick on the clutch or roll forward a little the hunting starts again.

Only happens when the car has been sitting for a long time, eg overnight or all day and then come back from work and turn it on. If the car gets to operating temp and then I turn it off for 1-3 hours and the engine is still pretty warm no issue, idle is perfect.

Now before I start playing with the TPS voltages and mucking around pulling apart things I'm wondering if this is just something in my maps in the low load/idle section that needs adjusting as it only happens for ~10 degrees so I would have guessed the voltages on the TPS are fine? Car has been tuned a number of times many years ago by a very reputable tuner.

It happened as soon as I swapped the standard ECU to the powerfc and it has been like this ever since, even with adding in cam gears and a z32 AFM. I have used contact cleaner to clean the AFM and I've cleaned the AAC with throttle body cleaner and ear buds in every little knook but no avail.

Any suggestions?

I've found this post from long ago which seems almost identical so I'll give turning off O/2 feedback a go (not sure if it's enabled currently or not) but wanted to see if others had the same issue?

 

Thanks.

 

 

 

Link to comment
https://www.sau.com.au/forums/topic/467745-rb25det-pfc-idle/
Share on other sites

May well be the AAC - the water heat heated idle valve starting to close at that temperature.  That's not the problem, but the trigger for the problem.  I would then guess that the IACV is dirty enough to not be responsive to the ECU's commands and so the ECU loses control of the idle.  When it drops too far the ECU throws the valve open more and it suddenly is too much valve and the idle rises too far and it throws it shut.  The ECU might also be pulling and re-adding timing to gain control.  (I don't know if PFCs retain that ability).  Rinse and repeat until the car is warm enough that it settles down.

So it may just be that you need to dismantle and clean the IACV.

Edited by GTSBoy

Mine idled like crap when I changed to larger cams and my tuner tried a few different things and couldn't get it to idle right, 650-1200rpm. I tried different clean IACV's, disconnected the plug and tried resetting it, tps voltage and nothing really helped.

I played around with the idle settings in the hand controller and it as a slight hunt for about 20 seconds and then idles at 800rpm, I have a lightened flywheel witch I do believe was causing the excessive hunting with the old idle values but its mint now. Ill be going back to a standard flywheel soon, not because of the idle hunt but more because its a pain in the arse to drive but I'm interested if the start up hunt still follows or not.

Thanks guys,

I've cleaned the IACV multiple times, let the throttle body cleaner really get in there and then scrubbed every part of it with cotton ear buds until the buds came out clean ( took like half a pack) let it dry, installed it and no difference. If I'm honest, the only thing i noticed was the hunting was slightly more aggressive then when it was dirty but that was about it.

Perhaps buying a second hand one to test with might be needed.

 

 

So I checked and the O2 sensor was enabled, disabled it, made a slight difference, the hunting was less aggressive, as in it didn't rev up and down as quick but it was still doing the same thing so I put it back for now because it didn't stop the issue.

Then I used the sensor check on the hand controller and found the TPS idle was a little low for idle. 0.35v closed, 4.18 WOT.

I've now adjusted it to be 0.44v closed (every time I got .45 then tightened it moved), and 4.24v WOT.

The car is warm so wont be able to check till the morning but when I did turn it on the idle *seems* smoother already.

Any issues foreseen with WOT 0.06V+ more then before affecting my tune etc?

 

My tps voltage was about the same as yours, I set it as it should be and I think it may have played apart in helping it. Adjusting the tps wont affect the tune, you are only telling the computer what position the throttle plate is at.

  • Like 1

Ok so I took it for a decent drive today. Definitely a big improvement.

It's hunting less aggressively and the revs aren't dropping as much - instead of dropping from 1500rpm - 900rpm and back and forth it's now only dropping to 1200rpm and back to 1500rpm slower.

So what's happening now:

10deg-59deg high idle (1500RPM) stable idle, 59deg-71deg hunting still, but no where near as bad and only 1200rpm-1500rpm, 71deg+ normal stable idle at 900-950rpm.

So the questions I have:

- Is there a way to adjust that 1500rpm cold idle to sit at 1200rpm when cold to fix the last problem? Where to start - the Idle screw in the IAC? But that would adjust my idle overall. 

My idle settings in power fc are fine as far as I know :

rev limiter 7200

f/c A/C 1100

f/c A/C 1000

idle A/C 900

idle A/C 900

- Should I try to adjust the TPS above 0.45v for idle to bring it up to 1500rpm when idling cold? or safer to leave it where it's at now?

-Any other thoughts? I am already much happier with the result and reckon I can live with it now but would be good to fix it overall if it's just a matter of fiddling.

 

Thanks.

 

Good to hear you are making progress. I'd be playing around with the iacv once it's warm, search for the thread and I believe that should sort it out.
If I get a chance today I'll have a look at my idle figures and compare, but every car is different.

Johnny, thanks, will have a fiddle, I have wondered if that would help.

Ad's. appreciate if you could compare values, I know each car will be different but to get an idea if mine is in the ballpark like I did with the TPS would be good. Would it be best to adjust IACV when car is in the hunting rev range or wait until it's at full operating temp?

89Cal, I'm not sure, been so long since it was done, I don't have a datalogit cable to backup the tune/reload otherwise I would do a new idle learn.

I can have a look and let you know, I have larger cams in mine so not entirely sure if mine will be any help if it affects it the idle at all.

From memory (might not be correct) you need to let the car warm up to normal temp, disconnect the tps plug and wind the idle screw until it idles at 850-900rpm then connect it back up.

If I had a datalogit I wouldn't mind doing my idle re learn again and hoping it fixes my minor hunting on start up, but considering mine is running e85 I let it warm up before moving anyways.

Hey guys, final update.

Decided to take the car into work this morning (cold morning, stop start traffic for over an hour) used to be the worst scenario to make it hunt and rev a lot.

All is perfect. Was great drive in, just purring while stationary the whole way so I'd say it's fixed!

I did end up adjusting the fuel cut a bit which is what fixed the last bit of revs issue.

So now my settings for Idle on the power fc are:

rev limiter 7200

(aircon Off) f/c A/C 1110

(aircon ON) f/c A/C 1100

(Off) idle A/C 900

(On) idle A/C 900

I previously had the 1100 and 1000 I said earlier around the wrong way.

So now what happens is high idle from 10 deg->68/69 deg (1500-1700rpm, but smooth), once past 69/70 idles at 900-950rpm. that's it, perfect and smooth.

 

So as a summary the steps I did to solve the problem:

1. Adjusted the TPS to read 0.45v on closed

2. Raised the fuel cut with no air con from 1000 to 1110

 

Other things that may have helped:

1. Cleaning the IACV with Carby cleaner a couple weeks ago

2. Turning the O2 sensor On/Off to see if the O2 sensor was dead, my sensor is now ON and appears to be fine.

 

Thanks for all the great help as always.

 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
    • Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
    • But first....while I was there, I also swapped across the centre console box for the other style where the AV inputs don't intrude into the (very limited !) space.  Part# was 96926-4GA0A, 284H3-4GA0B, 284H3-4GA0A. (I've already swapped the top 12v socket for a USB bulkhead in this pic, it fit the hole without modification:) Comparison of the 2: Basically to do the console you need to remove the DS and PS side console trim (they slide up and back, held in by clips only) Then remove the back half of the console top trim with the cupholders, pops up, all clips again but be careful at the front as it is pretty flimsy. Then slide the shifter boot down, remove the spring clip, loose it forever somewhere in the car the pull the shift knob off. Remove the tiny plastic piece on DS near "P" and use something thin and long (most screwdrivers won't fit) to push down the interlock and put the shifter down in D for space. There is one screw at the front, then the shifter surround and ashtray lift up. There are 3 or 4 plugs underneath and it is off. Next is the rear cover of the centre console; you need to open the console lid, pop off the trim covering the lid hinge and undo the 2rd screw from the driver's side (the rest all need to come out later so you can do them all now and remove the lid) Then the rear cover unclips (6 clips), start at the top with a trim tool pulling backwards. Once it is off there are 2 screws facing rearwards to remove (need a short phillips for these) and you are done with the rear of the console. There are 4 plugs at the A/V box to unclip Then there are 2 screws at the front of the console, and 2 clips (pull up and back) and the console will come out.
×
×
  • Create New...