Idle Problems Rb20Det

[D.I.Y. Mik]

So i cleaned out my aac valve and its still hunting at idle and dipping a lot with power loads(fan, steering).

When i first got this car i didnt know about setting the idle on the aac valve and i used the little screw to open the throttle slightly.

Does the throttle need to be fully closed/sealed for it to idle properly? Is this in effect an air leak as far as idling is concerned?

Also the computer idle screw is set to full low, all the way counter-clockwise.

[ima_slap_joO]

Hey mate, first you will probably want to check your TPS is set correctly, so just double check that is reading .48 volts at idle, if not adjust and reset the computer. Once that is set, if your IACV needs adjusting you should just be able to turn the idle control screw and this should alter the idle speed as soon as you start turning, if this does not occur you may have an issue with the oxygen sensor (my IACV would not alter the idle speed AT ALL with the oxygen sensor plugged in, turned out it was not wired correctly, but once disconnected or wired correctly, the IACV once again had become operable with the idle screw). The screw head should only need to be pretty much flush with the outermost part of the housing, not in too far or out too far. Just make sure you give the IACV a really good and thorough clean as once the carbon builds up on the black diaphragm this adds friction and does not allow free movement once the valve is moving.

You should also return the throttle? screw to the standard position, the less variables, the more likely you are to find the actual problem.

Why did you clean the IACV? Did you have idle issues previously or? I had idle problems for close to a year, both the TPS setting and the 02 sensor had a massive part to play in rendering the IACV useless, only once I had both the TPS and 02 sensor working correctly did all the idle issues go away, but it was instantly, as soon as the other interferences were gone.

[D.I.Y. Mik]

Thanks thats helpful, but..

How do i test the tps? (.48 v from where?)

Also the idle does seem to adjust slowly (delayed reaction). So theres an issue somewhere.

Can i clean my O2 sensor?

Ha! this is like science, the answer to one question leads to two more questions and so on ad infinitum.

Ps. thanks for help.

[StevenCJR31]

Kudos motorsports have new 02 sensors for RB20DET ($77) so dont worry bout cleaning old sensor

[D.I.Y. Mik]

Yes always had idle issuesWhat exactly is the IACV? is that the AAC?

Theres no diaphragm in my AAC, just a soleniod, spring and valve.

it must be the old type.

[ima_slap_joO]

Hey mate, the TPS throttle position sensor is a little black box with a plug which sits on the throttle body, there is a plug right facing, and three wires which come out the bottom of the unit, you need to measure the voltage beween the middle and right facing wires of the three wires out the bottom, it should be around .48v at idle, and move up to around 5.v at wide open throttle, if you havent played with this it may be ok, you can also test this on reds without the car on. The valve you are playing with at the back of the plenum there is the idle air control valve, and you will need to ensure all the soot is gone before trying again, take the whole unit off, including the silver housing and give it all a good clean. You can unplug the 02 sensor while trouble shooting the TPS and IACV.

[ima_slap_joO]

Yes always had idle issuesWhat exactly is the IACV? is that the AAC?

Theres no diaphragm in my AAC, just a soleniod, spring and valve.

it must be the old type.

May have used the wrong term haha just clean everything, and ensure its back together properly.

[D.I.Y. Mik]

Ok, closed the throttle completely, re-adjusted the idle on the aac(iacv) now its fine, responds well to power loads and no hunting.

Tps must be ok too, thanks for the exact info on how to test.

That info should be saved for others. or put in diy/faq.

I read somewhere that SAU is the best skyline resource on the web and if you search you know its true.

[D.I.Y. Mik]

Its still playing up! dagnabbit.

On a cold start it idles at 1100 then over a minute it climbs to 1900 then drops suddenly back to 1100.

If i restart it idles at 850.

thats bad for a cold engine, i can hear funny noises when i switch off to restart.

Any ideas? im stumped.

[ima_slap_joO]

Hey mate, I believe that is just the engine attempting to reach operating temp quickly as possible. Let it warm up, allow it to drop to 1100 RPM then adjust the IACV. I actually idle at around 1000 RPM anyway, helps with the brass button clutch and stalling. BTW, have you still got the original BOV working or replaced with after market atmo BOV?

[DVS JEZ]

Make Sure the throttle screw is set and the TPS is set correctly. If the tps is incorrect the ecu wont run the idle maps