Jump to content
SAU Community

Recommended Posts

98 ER34 GTT idle races, if AAC is unplugged, then idles perfect.

 

1998 ER34 GTT rb25det neo, 

rpm's race at idle, around 1200 rpms, I cleaned MAF, AAC/IACV. no change.

if I unplug the ACC 2 wire plug, it idles correctly, around 900 rpms.

 

questions:

1. will it damage anything or effect characteristics by driving the car with this AAC unplugged?

2. is this 2 wire AAC component replaceable, or must one replace entire IACV assembly?

 

appreciate any help

Edited by JC71

The "2 wire AAC component" is just a solenoid, that opens and closes the idle control valve. It's PWM controlled by the ECU. It is hard to see how you can have the symptoms that you describe without it being caused by the valve itself being dirty and so not moving smoothly. Yes, I understand the rest of your description.

Will it hurt to have it unplugged? No. You will not have idle control so idle speed will be able to fall below stall point if and when you put too much load on it (AC on, PS turned to one side, etc).

Is it replaceable? I dunno. I think if mine ever goes that bad I will just be doing the whole ECU. Good excuse to go e-throttle and sidestep the whole idle control bullshit circus anyway.

  • 3 weeks later...

I replaced the entire IACV assembly with new unit from Nissan, idle acts the exact same, starts and runs with idle rock solid at 900, as soon as I plug in the solenoid from the new IACV the idle races up to 1400, even with idle adjustment on side back of intake manifold maxed out for lowest idle still way too high around 1200.  Again if I unplug the IACV, turn idle screw to about half and it runs fine at around 900. thinking about just leaving it unplugged, do not ever plan to drive it when its cold, and always stored in climate control garage, just sucks to spend 500 dollars and have no change, could have left the original at this point. any other thoughts as to what it could be? maybe not even worth pursuing? that is if cold start idle aid was the only reason for Nissan to have this part anyway. tried AC and other loads and it never seemed to push idle below stall.

Yeah, that doesn't necessarily mean that it flows. If the exit side pipework is blocked somewhere (in the hose, in the nipple that it returns into the motor/plumbing, etc), but the supply side is not blocked, then when you crack the bleeder you will get flow from the open side. But when you close the bleeder - no flow. And.... therefore no heat.

You might have to work a little harder to prove it to yourself. When I bought my engine the entire IACV bleeder was choked with cooling system schmutz. I had to clean it and the pipework out before it would work.

11 hours ago, JC71 said:

I replaced the entire IACV assembly with new unit from Nissan, idle acts the exact same, starts and runs with idle rock solid at 900, as soon as I plug in the solenoid from the new IACV the idle races up to 1400, even with idle adjustment on side back of intake manifold maxed out for lowest idle still way too high around 1200.  Again if I unplug the IACV, turn idle screw to about half and it runs fine at around 900. thinking about just leaving it unplugged, do not ever plan to drive it when its cold, and always stored in climate control garage, just sucks to spend 500 dollars and have no change, could have left the original at this point. any other thoughts as to what it could be? maybe not even worth pursuing? that is if cold start idle aid was the only reason for Nissan to have this part anyway. tried AC and other loads and it never seemed to push idle below stall.

You definitely have a big problem if with the adjustment screw closed up you're idling at 1200 rpm. Have you verified you have no vacuum leaks? No throttle shaft seal leaks? Nobody has messed with the throttle body set screws? I would love to see what Consult reports when your engine is idling that high.

I recall you're going to launch the OEM ECU into the bin in another post, unpopular opinion but throw the AAC, IACV, cable throttle & pedal all into the bin and convert to DBW e-throttle & pedal.

For quick install (minimum fab work) these guys have a great bit of kit:

https://outsidergarage.com/products/nissan-rb25-oem-dbw-conversion-kit

Hit up @outsidergarage for more details.

(I'm not affiliated nor do I use them)

9 minutes ago, Dose Pipe Sutututu said:

I recall you're going to launch the OEM ECU into the bin in another post, unpopular opinion but throw the AAC, IACV, cable throttle & pedal all into the bin and convert to DBW e-throttle & pedal.

For quick install (minimum fab work) these guys have a great bit of kit:

https://outsidergarage.com/products/nissan-rb25-oem-dbw-conversion-kit

Hit up @outsidergarage for more details.

(I'm not affiliated nor do I use them)

Sure, but personally I'm a big fan of when you have a problem, don't make it harder to diagnose by changing more variables all at once.

54 minutes ago, joshuaho96 said:

Sure, but personally I'm a big fan of when you have a problem, don't make it harder to diagnose by changing more variables all at once.

That's perhaps not even correct in this instance though. If the OP were in fact to bin all that troublesome crap and convert to DBW, and then if the problem persisted, we would at least know that it was not caused by any of that troublesome crap and he could go looking for it in more likely places. AND... he would have a significant upgrade in niceness to go along with it!

  • Like 1
1 hour ago, GTSBoy said:

That's perhaps not even correct in this instance though. If the OP were in fact to bin all that troublesome crap and convert to DBW, and then if the problem persisted, we would at least know that it was not caused by any of that troublesome crap and he could go looking for it in more likely places. AND... he would have a significant upgrade in niceness to go along with it!

Sure, but you could just pull enough timing out of the map to make it idle at whatever RPM you want. Or close the throttle until it's about to bind to compensate for vacuum leaks.That's kind of why I'm not a fan of this approach, especially if OP isn't experienced at tuning these things.

I couldn't get this to work right, New clean IACV, coolant seems to flow and solenoid functions, but again as soon as I plug it in the idle raises, I ran the car for a good 1/2 hour messing around with various things it, no vac leaks.

At one point with the IACV plugged in I was able with the adjustment in the side of IACV turned all the way in get it idle down a little to around 1000, but no lower, and it would surge, I unplugged the IACV engine rpms drop to about 350, turned the adjustment about 3 turns in , set idle to around 800 rpms' and it idles smooth.

I set the idle stop screw abut the same so it cant drop below under load. the engine starts, restarts, with no load or with a load seems to run fine. I will have to leave it like this for now as I cant get it to function correctly with the IACV plugged in.

One other thing I discovered that might be the reason for some of the issues, the engine in the car is a RB25det neo from a Stagea along with the Stagea ECU. so alot of wiring, plumbing etc that is typically there in a R34 is not. 

Spray carby cleaner around all gaskets and other possible vac leak locations on the inlet manifold. See if the revs change somewhere. If so, vac leak found.

 

Plug in Consult and see what the ECU says it is doing to the IACV. It will tell you how many "steps" it is commanding it to open. If it is not commanding it to open more than normal, then the problem is elsewhere. If the ECU is trying to drive the IACV really far open, then you know that it is either ECU cray cray or some input to it telling ti be stupid.

14 hours ago, JC71 said:

One other thing I discovered that might be the reason for some of the issues, the engine in the car is a RB25det neo from a Stagea along with the Stagea ECU. so alot of wiring, plumbing etc that is typically there in a R34 is not. 

can you check if this is an auto ECU?

 

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

    • I would just put EBC back on the "I would not use their stuff" pile and move on.
    • Can I suggest you try EBC directly again and link them to as many competitor catalogues as you can to show their listing is incorrect, eg https://dba.com.au/product/front-4000-series-hd-brake-rotor-dba42304/ If you have access to an R33 GTST VIN and your VIN, you could also use a Nissan Parts lookup like Amayama to show them the part number is different between 33 GTST and 34 GTT which may get their attention
    • So i got reply from EBC and they just this site where you can clearly see those 296mm fronts on R34 GTT. I send them photos and "quotes" that 296mm are not for 34 GTT and they are too small. But it will be very hard to return them cuz nobody here knows 100% and they just copy those EBC catalogue :-D https://ebcbrakesdirect.com/automotive/nissan/skyline-r34
    • Hi, is the HKS  Tower Bar still available ? negotiable ? 🤔
    • 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.
×
×
  • Create New...