high idle and hunting

[Rome32]

So my car(r32 gtr) is idle hunting and is idling at around 1200-1350 +/- 50 and it stallings out every now and then at idle.i brought it to a shop to check it out and they said ithe problem was both o2 and the aacv and iacv. what are my options as far as o2 that i can buy i have a rb26 from an r32. also i took out the accv and cleaned them(i have 2 one from my spare motor) and the idle is till high?? and stalling out.

[bobbo]

Oem ecu?

[Rome32]

yes and tuned on stock turbos making the usual 360whp basic setup. vacuum is good no leaks found in test

[Rome32]

what o2 should i go with oem? or after market if so what kind? and any part numbers would be great

[Skym]

Stalling is most likely the TPS is faulty or not set on idle contact. The idle contact, WOT contacts tend to bend over time and the peak voltage drops. If TPS is not on idle contact the stock ECU doesn't switch to the kick down tables to raise the rpm so the engine doesn't stall, idle stabilisation tables, etc.

You'll need to buy a new TPS every 40-60,000km (how long they last depends on how the car is driven), about same km as o2 sensors (routine maintenance)-

http://www.kudosmotorsports.com/catalog/genuine-nissan-pitwork-throttle-position-sensor-tps-nissan-skyline-r32-gtr-r33-gtr-r34-gtr-stagea-wgnc34-260rs-p-585.html

When there is a TPS problem, some people raise the idle rpm to help prevent the engine from stalling.

You need to set the ECU into idle rpm adjustment mode, disconnect the AACV valve plug (so engine ECU doesn't adjust the idle rpm) and adjust AACV screw to around 1000rpm (higher if have aftermarket cams installed). Then plug AACV plug back in and see if idle rpm stays the same. If it does, set engine ECU back to run mode. If not, repeat until it is set correctly.

This is easy via Consult (Nissan's diagnostic computer) or Conzult software + cable or even Nistune software + cable, as you can see idle rpm accurately, but you can do it via the diagnostic pot / screw on the side of engine ECU (turn all the way to the left from memory to enter idle rpm adjustment mode). Note how many amount of turns from run position, as you have to set it correctly back to run after you have finished adjusting the idle rpm (otherwise the cat overheat light / engine check light will flash on the dash when hit bumps in the road, etc as it switches between diagnostic, run mode). Also note turning to the right can adjust idle rpm 200 rpm or so at a time, so I think AACV has to be unplugged until screw / diagnostic pot is set back to run.

You might want to put a bit of twink to note which side of the head of the screw / diagnostic pot should be facing the run. The run mode should be indicated on the marks surrounding the screw / diagnostic pot (grey? sticker) on the sde of engine ECU.

You'll need to remove the kick panel in the doorway (remove the screws), kick panel cover (remove the screws) under dash that protects the engine ECU. Then unbolt the engine ECU while being very careful not to pull on the main loom too much (the wires are easily pulled out of stock plugs and causes the engine to playup, etc).

When AACV fails the engine won't idle at all.

Stock o2 sensors are NTK brand (Nissan etches their logo onto them, but are the same sensor) -

http://www.kudosmotorsports.com/catalog/ntk-lambda-oxygen-sensor-ntk-otd2f1p-nissan-180sx-rps13-silvia-ps13-skyline-r32-gtr-rb26dett-sr20det-red-top-p-1024.html

Like they said in the link, you'll need to reuse the original plug from the o2 sensor on the car to use it as the front o2 sensor.

If don't want the hassle of changing the plug, buy genuine Nissan o2 sensor for the front or both from Nissan. Nissan part number should be on the o2 sensor itself, etched onto the side of it (same with nearly all of Nissan sensors / parts).

[Rome32]

so i have changed both o2 with oem parts. also bought a new oem tps. and have unplugged the iacv and set the screw in all the way so the idle sits at about 1080 rpm at warm.It runs smother and idle hunting is much better. but still stalls randomly at idle??? and if i blip the gas at a stand still it bogs very slightly when i pull off the gas just before it gets back to idle(no throttle) what else could it be?? could the have anything to do with the tune?

[bobbo]

Have you ever cleaned the MAFs?
Do you have a wideband? I'm curious as to what your A/F ratios are doing when it's acting up.
What do you have the TPS set to for voltage when at idle?

[Rome32]

i just plugged the tps in right out of the box. how do you set the Tps voltage? i will clean the mafs. and see what that does my wide band sensor is not working very well so i can't really rely on it much :S is there a proper way the clean the MAFS?

[bobbo]

To set the TPS you'll need to use a volt meter. The method is in the service manual. If you don't have one a quick search on the Internet will get you a copy. It's a must have. You're looking for ~.48-.5 volts.
To adjust it you loosen the same two screws used to secure it in place and clock it SLIGHTLY one way or the other to get the desired value.
To clean the MAFs simply go to your friendly neighborhood parts store and buy some off the shelf MAF cleaner. Once your MAFs are removed spray the crap off the element inside of them. Make sure your filter(s) are clean too.
Good luck!

[Skym]

If don't set the TPS on the idle contact the OEM ECU won't kick the rpm up (use the kick down tables, etc) and the engine can stall, especially if put it under load (lights, aircon, going up and hill) and back off throttle quickly.

This is easy via Consult as the idle contact light lights up on Consult (Nissan's hand held diagnostic device). If have Nistune this has the same feature in the tuning software, so is fairly easy to set.

Via multimeter at the TPS plug is the other way, but via Consult or Nistune is best. If have Nistune installed, only can use Nistune tuning software.

[Dragon Humper]

Having the TPS set right on the money will make drivability sooo much better. I drove mine around for about 10 min. with it set too low (so that the idle indication "off" on the consult was delayed by quite a bit) and it stumbled badly everytime I got on the gas to go. With it set so that the idle indication was never "on" it ran super rich and hunted a bit. I was running without MAFs though, with, it would be worse. Clean those MAFs too, will help a bunch.


Jon.