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High Idle

Tristan21

By Tristan21,
in General Maintenance

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Tristan21 Contributor

Tristan21

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RB20DET

After cleaning and re-installing the AAC Valve, the idle now sits at 1400rpm, higher when cold. Before cleaning the valve, the idle was 800-900rpm.

I have spent days reading through posts and trying to find a solution.

So far I have tried...

1. Adjusting idle screw (turned all the way in)

2. Reset ECU

3. Removed and cleaned IAC Valve

4. Re-gapped spark plugs to 0.8mm

5. Insulated coil packs with silicone

6. Checked all lines and connectors

After cleaning the IAC Valve last night, this morning the car was idling at 2000rpm all the way to work. It finally dropped after driving for 20 mins to 1600rpm. I noticed the spring inside was not fully closing the valve, obviously allowing some air to enter on idle. I presume this may contribute to the problem.

The only other problems I can think of is;

1. Gasket on AAC valve is faulty

2. Vac leak in or around plenum/manifold

3. Faulty TPS

I thought I might try adjusting the CAS but I wanted to post here first to see if anybody might be able to pinpoint the problem.

Any help would be appreciated, cheers.

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jiffo Mentor

jiffo

Posted
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You say it was idling at reasonable RPM prior to you cleaning it, and after the clean it's too high.

If the only item you've touched is the AAC valve, why go looking at other parts?

Usual culprit for high idle is the air reg but you haven't disconnected its plug or removed its hoses have you?

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Tristan21 Contributor

Tristan21

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I thought the problem may have existed prior to the AAC Valve becoming dirty and that cleaning it improved air flow allowing a leak to cause high idle, thats why I was checking other parts. The AAC Valve was in good condition and the spring was tight, the only other thing I can think of is that the gasket may need replacing, could this cause high idle?

I havent removed any other plugs or hoses without replacing them, however i dont know what the air reg looks like or where is it located.

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Tristan21 Contributor

Tristan21

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it could be the gasket .. did you damage it during the clean ? if so replace it. Also check that the throttle cable sits correctly .. if it doesn't revs will be up and its easy to miss

Its probably a combination of both to be honest. I also beleive the regulator assembly is stuffed as the spring dosent hold the metallic plate over the gap fully, allowing air to enter on idle.

I have ordered a new valve from Nissan and will check the throttle cable and valve gaskets.

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