Wonky Idle

[TheyKilledKenny]

If I decide to bypass tps, I can just connect the 2 vacuum hoses with connector pipe I guess.

Think you mean to bypass the IACV.

I played with my tps today and just about completely fixed my idle. I used an old analog multitester and its not very accurate, I probably got it fairly close to .48v. The car went from 1500rpm to about 1000rpm, then I adjusted the AACV to compensate. It was weird setting it though. I first started the multitester with the DC current at "10" increment setting, when I set it to .50v with this it did barely did anything to improve idle. I went to home depot to grab some nuts and bolts for my side skirt project and decided to take a gander at digital multitesters....$100. Went to crappy tire and $20 later I was on my way back to the storage unit. Damn thing needs a 9v battery. Weird thing was I then continued to use the analog except in AC current "10" increment setting, thats when I got it close to proper idle. Obviously Im going back with the digi to fine tune, but why would AC even come up? I thought cars produce DC current and not AC. I guess the alternator produces AC but then rectifies it to DC, so why would it show up....Im confused.

[Skym]

You are meant to put ECU into idle adjustment mode, remove AACV plug and adjust AACV and then plug it back in and if ok, put ECU back to run mode. If idle rpm is not set correctly, idle rpm can fluctuate up and down by around 1000rpm.

Most of the time it's the o2 sensor causing missing, slight idle fluctuation at idle or airleak.

[TheyKilledKenny]

I went back today with the digital multitester and was amazed to see that I set the TPS to .488 with the analog, not bad. Now my idle is way too low, Im idling at like 650-700. I tried to change the idle following insu's guide on SAU. I let it warm up then unplugged the brown connector on the AACV and attempted to change the idle. My idle never really changed when doing this. When I disconnected the two plugs to the TPS then adjusted the AAC adjustment screw it actually changed the idle, but returned to a low idle once I reconnected all the looms. I tried adjusting the screw on the ECU but it does little to nothing to affect my idle. Should I attempt to set my TPS voltage higer than .500? Would displacement or timing have an affect on this because I have high lift cams and a bored out block? Could my TPS be losing its contact points? It sounds decently healthy for idling at around 700, but I would feel more comfortable with it around 900 RPM.

[TheyKilledKenny]

The car went from 1500rpm to about 1000rpm, then I adjusted the AACV to compensate.

This is misleading in my last post. I meant to say that I improved average idle from 1500 to 1000 just by setting the TPS, then adjusted the AACV to compensate down to 900. I need to be more specific.

[Skym]

The AACV to ECU part is so they are both set at 650rpm (stock cams). Once you have them both set to be at the same idle rpm (650rpm), then idle rpm can be adjusted via idle rpm table on ECU. If you have cams, idle rpm should be set higher. But it depends on spec of cams as to how high you set idle rpm.

When TPS is set correctly, TPS idle contact light should light up. That's why you need Nissan's Consult (handheld diagnostic computer) or software on laptop (Nistune) that allows you to set TPS, as TPS idle contact light light's up.

The problem with R32 TPS is the idle, WOT contacts can bend over time. So the position of idle contact, voltage can change over time.

[TheyKilledKenny]

Yea I was reading that R33 RB25's idle at 650, so Im probably not far off for a stock idle. I sourced a nistune dealer and installer about 3 hours away in Calgary. I wonder if Nissan dealers here could adjust my idle tables with their consults here in North America. Im not planning on getting nistune until I drop in bigger injectors, turbo, and install a fmic. Maybe Ill just get nistune earlier and learn how to use it.

[Skym]

It says 650rpm on idle rpm table. If coolant is not up to operating temp, engine can idle higher.

Nistune can be installed before, as it uses the same maps, tables, etc as your cars ECU has now and will run the same. What you do is download all the maps, tables to a 32kb .bin file with Nistune tuning software, PLMS cable and then send to Nistune dealer or Nistune in Australia and they will transfer to Nistune board. Once you install Nistune board, etc it should run the same as it does now. But can change settings on maps, tables, etc. Basically you don't need to tune ECU straight away like you do with aftermarket ECU's.

Even without Nistune installed inside ECU you can still set TPS, set idle rpm, download maps and see what tables, maps ECU is looking at in realtime, etc. Then read documentation and understand what this feature and that feature does, etc.

Only problem with Nissan's Consult is they need to have the cartridge for your model of car.