Hi, I'm just sharing my experience in case it helps anyone with similar issues after cleaning or replacing the dual throttle bodies and can't seem to do the Idle Air Volume Learn procedure.

I cleaned my TBs, the idle would then hunt between 1200-2000. I eventually bought second hand, uncleaned replacements, which after a week or so after replacing, the idle hunt stopped but it was still idling way too high.

From what I gathered, the issue doesn't seem to be related to damaging any of the components in the original TBs, as some suggest. It's purely the increased airflow which mismatches what the ECU has learnt. This can cause either high idle or idle hunting, depending on the % of airflow increase since before the TBs were cleaned.

It may be possible to manually adjust the screws to tighten the closed position of the butterfly valves to simulate having less airflow, enough to stop idle hunting at least. As long as it's not idle hunting the ECU may slowly learn the idle air volume (which it seemed to do on mine after several weeks) and slowly drop the idle revs, hopefully enough to at some point do the relearn procedure.

If your dealer works on Infinitis or imported Nissans they can do the relearn using the Consult software, but often even they may have issues saying the relearn won't take. In this case you can ask them to reflash the ECU to version C. In my case the Nissan dealer wouldnt even touch my car since it was imported so I had to do it myself. If they say you need new TBs they probably don't know what they're talking about.

With regard to doing the relearn procedure yourself I recommend getting the NDS III or II app (whichever is suited to your car) and a compatible OBDII Bluetooth adapter. I bought a cheap adapter on ebay but it didn't work because it didn't have all the protocols, so I bought a more expensive one (about $70 AUD) from jaycar which worked. It has an IAVL button which is an absolute must if you've tried the pedal dance a few times and it doesn't work. You can also check the metrics such as temp, revs etc. which is useful for making sure that the parameters are met.

But, as many have experienced it's not that simple, since even though you seem to have the parameters (see screenshot) met, it seems to flat out refuse to work and just infinitely keep counting. I tried unplugging some fuel injectors which brought it below 850 rpm which is apparently the upper limit of what's required to perform the procedure, but even that didn't work. FYI to try this (since it has worked for some), first drive your car for a solid 15+ minutes (recommendation is 10m or more), and make sure the transmission is warmed up too not just the engine. Disconnect the negative on the battery, take off the engine cover and remove the bolts of the plenum enough to lift it, then unplug 2 or 3. Put the main bolts back in the plenum before starting the car, I left the two end ones off. Perform the IAVL (mine didn't work), then plug and bolt in everything the way it was.

So with that having failed, I drove the car around as normal, and noticed that eventually the idle speed would slowly drop, I'm guessing because the ECU has an inbuilt mechanism to learn the air volume over time, since this would be needed to account for carbon build up etc. It just took several weeks for it tevebtually idle below 850rpm (which is still more than the ideal 650rpm). I tried the relearn procedure several times after having driven it, and idling below 850 but they didn't work, even with seemingly all the parameters met (steering wheel straight, idle, temp, electronics off, hand break etc.). I even tried it stopped in reverse and drive gears too to lower the rpm slightly.

​​​​But I would after every drive or two try the relearn when I got home, and today it just happened to work, even though everything seemed the same as every other time.

​​​I don't know if there's anything in there that's useful but here are some takeaways that I got out of the experience:

• Get the NDS app if you've tried the pedal dance and it isn't working, this will save you so much hassle.
• If your dealer says they will work on your car (some don't if you have an import) they can reflash the ECU to version C and then perform the relearn, which seemed to work for many.
• Goal #1 is to get it to stop idle hunting if it's doing that. I replaced my TBs with uncleaned second hand ones which did the trick, but you may be able to temporarily tighten the butterfly valves using the screw on top, and then slowly loosen them over time AFTER successfully performing the IAVL.
• There are a bunch of parameters that need to be met to perform the IAVL. I've attached a screenshot below from another forum with them.
• Also the guide states to perform the pedal position learn and TB close position learn first, but you should only need to do this once, or maybe again if you've disconnected the battery.
• You can try artificially lowering the RPM such as by disconnecting a few fuel injectors,to meet the Parameters. This has worked for some.
• The high idle *should* eventually drop over time, hopefully eventually below 850rpm. For me it took several weeks.
• The IAVL seems to often not work even if all the parameters are met. Many people, and myself included, have stated that they tried it many times and one day it 'just worked'.
• Start your car up right after it successfully learns and ensure it's still good after turning the car off.
• Attached is my NDSIII screenshot of the data display right before the successful IAVL.

I hope this helps anyone.

 

Thanks for the writeup. I recently got a hr Z and am about to do the same when I change the sparky p's. This mostly matches up with my research. Did you need to relearn the accelerator even with the OBD reader? Did you disconnect battery to clean TB?

I'd expect rough/high idle on any car after disconnecting the battery for a bit, so I wonder if most these issues can be solved just by cleaning and running the car for a while.

 

I did disconnect the battery before cleaning the TBs, but the main issue for me was that there was so much carbon build up, even a lot more than my new second hand ones, that the difference in air flow at close position was too much.

I'm not sure if using the app negates the need for having to do the accelerator pedal position relearn, I just performed it manually using the ignition on/off/on/off with the right timing etc. Same with the T/B close position relearn.

I'm not sure if tuning using a reflashed ECU could solve the idle issues (that would have been my last resort card). I called a few places and they seemed to indicate that it would, although for dual intakes one guy said that it can be a bit temperamental getting the right mappings. The air volume mappings are stored in non volatile memory but in not sure if this memory is overwritten when flashed, when remapped, or not at all.

I'd probably talk to a performance shop first too and ask them about how they remap the idle air volume etc. I know people whove had after market high flow TBs installed so this issue shouldn't limit what can be done.

If you're keeping the stock ECU maybe check if your dealer works on infinitis or imported Nissans. Because if needed you can get them to reflash the ECU to version C which takes the relearn much easier. In Australia the Nissan dealer I went to said they don't touch imports. Only performance tuning places will, but they usually use third party ROMs such as uprev.