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Adjusting The Idle Screw On The Aac (rb20det)

lows_13

By lows_13,
in General Maintenance

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lows_13 Mentor

lows_13

Posted
Posted

I cleaned out the AAC the other week and had the put the idle screw back in.

Will screwing it in decrease the idle or increase the idle?

Can it only be adjusted while the car is turned off or does the car need to be running while

its adjusted.

I tried to adjusted the idle screw while the car was running but the car would rev up and come back down to the same rpm as prior.

RANDY Veteran

RANDY

Posted
Posted

To set the base idle, I think you have to disconnect the TPS first. The revs should drop, and that is your base idle at which you can tune. The ECU does the automatic choke kind of action to keep it alive, or keep it high when cold etc.

I use a consult cable and software, and most of the software allows you to adjust the base idle.

Nozila Grand Master

Nozila

Posted
Posted

thats correct. disconnect tps, start engine. give it a couple of revs - up to bout 2- 3 grand, then adjust the screw accordingly. clockwise to increase idle, anti-clockwise to decrease idel.

ross80 Rising Star

ross80

Posted
Posted

And what is the tps? throttle position sensor? If someone could put up some photos, I would appreciate it. I have a rb25. Ive done everything else except this (cleaned and siliconed up coils, cleaned every sensor with contact cleaner, changed plugs 3 times) and the idle is still all over the shop and it hesitates at about 5000rpm when i put my foot down. It boosts up but something is holding it back.

The idle is all over the place, would that effect performance like I have described?

RANDY Veteran

RANDY

Posted
Posted (edited)

Well, disconnect throttle position sensor (big black box on throttle body)

start car

rev few times

adjust idle screw

check revs by looking at the dash. Should be 650-700rpm I beleive? Check the sticker under the bonnet somewhere.

turn car off

reconnect TPS.

Timing can be checked using SydneyKid's guide. He wrote it up as part of a timing belt change on a Stagea, look in the model-specific section.

No pics from me! I'm going to work in an hour or so.

Edited by RANDY
RANDY Veteran

RANDY

Posted
Posted

Back of the inlet manifold (plenum) there's a blocked off (yellow plastic) hole, and a pipe that runs to your stock boost sensor. Next to the yellow plasticy bit, there is a screw there.

I did a search and finally found the brilliant post that I was looking for!

http://www.skylinesaustralia.com/forums/in...opic=110431&hl=

RANDY Veteran

RANDY

Posted
Posted

5000rpm problem has it's own thread somewhere too. Turns out that 90% of the time it's due to hair-line cracks in your coil pack(s).

Aroldtite(sp?) seems to be the best compound for sealing the crack.

RANDY Veteran

RANDY

Posted
Posted

silicone? i'd be pretty tempted to do it with glue... silicone doesn't stick as well as i'd like it... fine for plumbing, but I think with heat and metal surfaces it may come loose?

No other ideas, sorry!

It completely misses for half a second to a full second when booting it, right? If so, it's the right problem for the solution, but it could be a number of other things..

Possibly fuel pump leaning out, or ECU retarding timing if you're running higher boost... too many variables. =-[

RB30-POWER Mentor

RB30-POWER

Posted
Posted

To clarify how you adjust the idle, i've written the correct procedure below as the RB25 and RB20 procedure is different.

On the RB20DET (as asked by the thread starter)

Make sure the car is at operating temperature.

Make sure ignition timing is 15deg btdc @ 650rpm.

Disconnect the AAC Valve connector to stop the ecu controlling idle.

Adjust the idle screw to 600RPM.

Clockwise will make it decrease (screws in blocking the bypass passage and less air means less rpm), Anti-clockwise will increase the idle (screws out opening the bypass passage more and more means more rpm)

Reconnect the AAC Valve connector and the idle should be approx 650rpm (+ or - 50rpm)

If the idle is higher, make sure the diagnostic screw on the ecu is fully anticlockwise as this can increase idle if not fully anti-clockwise

On the RB25DET (not asked by the thread starter)

Make sure the car is at operating temperature.

Make sure ignition timing is 15deg btdc @ 650rpm.

Disconnect the TPS connector to stop the ecu controlling idle.

Adjust the idle screw to 650RPM.

Clockwise will make it decrease (screws in blocking the bypass passage and less air means less rpm), Anti-clockwise will increase the idle (screws out opening the bypass passage more and more means more rpm)

Reconnect the TPS connector and the idle should be approx 700rpm (+ or - 50rpm)

If the idle is higher, make sure the diagnostic screw on the ecu is fully anticlockwise as this can increase idle if not fully anti-clockwise

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