Setting Timing RB20

[BrianV8]

Oh ok ic. I have tried adjusting the AAC valve but its adjusted as far as it will go. Were do i find that IACV valve? And how is it adjusted?

[Skym]

You need to set the mode at ECU before adjusting AAC valve. The non manual way is with Consult (Nissan's diagnostic computer).

On top of bottom half of intake plenum, just behind throttle body when looking at front of motor. There's a screw on IACV valve to adjust valve inside. It should be fully open when cold, slowly close when engine warms up. Then AAC valve controls the idle. The valve inside IACV valve sometimes gets sticky, plays up. Worst case is that IACV valve needs to be replaced. If you do remove IACV valve to clean it, might need a new gasket.

[BrianV8]

oh ok and i take it to set the mode at the ecu all i have to do is turn that screw all the way over from where it is. And i can set my timing by that too correct?

[Skym]

I think you turn screw all the way to the left on ECU. That's for low idle. Then disconnect the AAC valve plug to get rid of idle feedback. Idle should be below 600rpm when valve is fully closed (might need to adjust idle screw on your cars AAC valve). Turn screw on AAC valve counter clock wise until idle has risen to 600rpm. Then reconnect AAC valve plug and see if idle stays the same. Then need to reset ECU screw by turning screw to the right. I think it's just before you see the dot that's before the dot for diagnostic mode.

Actually, yeah, you can adjust idle rpm by I think was around 250rpm at ECU by turning screw to the right.

[BrianV8]

Awesome thanks, i'll try that and cleaning the IAC valve and let you know how that goes.

[BrianV8]

Well i cleaned the IAC valve and played around with that screw on the ecu. No luck on anything. Still really stumped what that high idle is.

[Skym]

Have you checked for airleaks around throttlebody gasket and intake gasket between intake manifold, head???

[BrianV8]

no i didn't. i checked all my lines for but not the gaskets. Putting straight propane from a torch or something while the motor is running tells you if there is a vac leak correct?

[Skym]

I think some use carby cleaner or something similar, which is not harmful to engine.

Also I was thinking if there was a airleak in intake manifold, it would be like opening the idle valve more, which lets more air into intake manifold and raises the idle. But I think one of the symptoms of intake manifold to head airleak is rough idling.

[love_boost]

do you have to do set the iacv while it is running and then reset the ecu?

[Skym]

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

[BrianV8]

So do i spray carb cleaner around the surface where the head and intake manafold meet? And if i do have a leak there should be a change in rpm correct?

[Skym]

Yes. I think the engine runs rough or idle changes.

[BrianV8]

ok i'll give that a whirl see what comes up. So stupid question. If it does end up leaking can i just crank the bolts or do i have to replace the gasket? Because i guess esentially it becomes a boost leak as well not just a vac leak

[Skym]

I think like GTR (RB26), it's a paper type of gasket, so needs to be replaced.

I don't know of any aftermarket metal replacement intake gaskets you can buy for RB20DET. Also I think there's is a gasket between the two halfs of intake plenum.