Setting Timing RB20

[love_boost]

Just make sure the screw is set, so IACV valve is fully open.

so turn it all the way to the left? im assuming or im not even sure were or if i can find a screw on the iacv.

unless we are talking aacv. i always screw around with the screw that faces the master cylinder. but never seems to change anything

[Skym]

Need to set screw on side of ECU before adjusting AAC valve screw. I can't remember which way you turn the screw on IACV valve.

AAC (Auxilary Air Control) valve. When you turn auxilary's on, like aircon, etc, AAC valve raises the idle to around 1000rpm.

IACV (Idle Air Control Valve). This raises idle above 1000rpm and brings idle downwards as the engine warms up. I think it's an automatic version of the dash mounted choke on older 80's Nissan's or old school classic cars that you press in as the engine warms up.

Below is a thread with photo of IACV valve on a SR20DET -

http://forums.nicoclub.com/zerothread/302985

The IACV valves are similar with air entering via big hose, exiting via small hose. The small hose connects to underside of top half of intake plenum on RB20DET. The big hose is a single hose off T fitting. T fitting is plumbed into the vacuum hose that goes from J pipe (intake pipe that goes over top of motor) to AAC valve that's on back of top half of intake plenum (RB20DET).

Should see the adjustment screw in this link below. There should be a similar looking screw on RB20DET IACV valve -

http://i130.photobucket.com/albums/p260/positron32/album2/IMG_1789.jpg

Underside -

http://i130.photobucket.com/albums/p260/positron32/album2/IMG_1790.jpg

Closeup underside -

http://i130.photobucket.com/albums/p260/positron32/album2/IMG_1793.jpg

[love_boost]

so there is no adjustment at all on the IACV? i know were the screw is on the AACV

now just need to find out which way to turn everything

[Skym]

Look at page 4 of this thread. I mentioned which way to turn screw on AAC valve.

There's a adjustment screw on the IACV valve, as shown in the above links. RB20DET IACV valve has a different shape but does the same job.

[love_boost]

okay well i am completley stumped.
i realy have no ide what the heck is wrong with my car .

for me it is either a lumpy idle, 1200-2000rpm up and down when it is running temp. or 2000 or so rpm

not sure which one i should go with :P

[BrianV8]

Ya i hear ya man having the same problem, i ripped out what i thought was an AIC valve but it didn't look anything like the ones in the pic. Cleaned it up still same problem, havn't checked the manafold gasket like skym was doing earlier. Been snowing all day here

[Skym]

The IACV in the photo's is for SR20DET. RB20DET IACV valve is located on bottom half of intake plenum, just behind the throttle body when looking from the front of car.

[BrianV8]

ya it has one vac line going in and another going out to the throttle body. I took that out ripped it in half. There was a little plate in there that had a spring in it. NO adjustment screw on it anywhere. cleaned it all up with break lean and no difference.

[love_boost]

okay so i was just looking at my tb and the thing that the throttle cable attaches to that controls the butterfly in the tb, that round thing there is like a bolt that looks like if you loosen it, it may let the butterfly close further so the idle is reduced, before i touch this is this what it actually does, i was thinking if i were to put my tps back to were the car runs good and smooth, just at 2000rpm and back the bolt off, have the aacv bassically shut all the way, if that would work?

i also advanced my timing very slightly maybe 3-4mm and that got rid of my missfire but then it idled at 2500rpm lol!

[Skym]

Yep, RB20DET IACV has a bigger vaccum hose from T fitting on AAC valve vacuum hose and the other smaller vacuum hose plumbs into the bottom of top half of intake plenum, near throttlebody. I was told by a Nissan mechanic that there was a adjustment screw on the side. It's interesting that there isn't one. Maybe he was thinking of SR20DET when he said it????

Sometimes the throttle cable needs to be adjusted. I think there's adjustment nuts on top of top half of intake plenum. It's so long since we adjusted the cable (about 2 years ago), but I think we did play with something on the throttlebody when adjusting throttle cable.

[love_boost]

okay well i didnt drive out to the shop and couldnt find my special screwdriver and i think it looks like a nut with a like flat head screw driver.

but i angled the tps with the connector pointing as high as it could towards the hood so it idles way lower with the throttle response is pretty jumpy and irradicate in lower throttle positions.

[love_boost]

okay im about to set my timing and just want to clarify.

i have to disconnect AACV so there is no computer controlled spark advance right?

the idle has to be 650? seems low to me? i am idleing around 900RPM now is that fine? i can always turn the screw on the TB down a ways and reset TPS to get it to idle lower. or anyone happen to have a diagram of the harmonic balabcer itself with the timing marks on it that would tell me which is which?

which line is the 20*BTDC? or 15*BTDC? which is better to set spark timing for? i hear both but i am unsure 15* would mean more power?

[Skym]

Disconnting AACV plug stops engine ECU playing with idle rpm.

From what I can remember, orange looking mark on pully is O degrees and every white mark to right side is 5 degrees apart.

Manual is 15 and auto is 20 degrees at 650rpm. ECU ignition maps are tuned to match base ignition timing, so is important that it's set correctly at CAS. Ignition timing will probably fluctuate between say 15, 19-20degrees with timing light. That's idle stabilization on ECU making the timing change between 0, 4 degrees. It makes base ignition timing hard to set and can be frustrating.

Also don't tighten one bolt then another on CAS. Tighten nuts evenly to hold CAS in place, turn engine off and tighten. One nut only can damage front of cam, bearings in CAS, etc.

Make sure engine is up to temperature before adjusting ignition timing.

[love_boost]

okay thank you skym i will have a closer look.

is my car always suposed to be idleing at 650? or only for the timing?

[Skym]

My cars engine always seems to idle around 800rpm. If you leave to settle, after a few minutes, idle settles at 650rpm.