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Idles high briefly when placed in neutral


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#1 8DC

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Posted 16 March 2012 - 08:19 AM

When i come to a long stop and place my '76 280Z in neutral, the engine races briefly for a few long seconds before settling back down into the normal idling range.

What could be causing this and how do I fix?
Thanks.

#2 ttodhunter

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Posted 16 March 2012 - 09:08 AM

It sounds like the BCDD valve, and it's normal to some extent. It's described in the FSM in the Emission Control section.

#3 NewZed

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Posted 16 March 2012 - 10:03 AM

Automatic?

#4 8DC

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Posted 17 March 2012 - 04:52 AM

manual 4 speed

#5 NewZed

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Posted 17 March 2012 - 09:30 AM

By "long stop" do you mean coasting to a stop? Is it your foot on the brake pedal when the high idle happens? Does the idle drop when you take your foot off the brake, and does it go back up when you press the brake again?

Could be the brake booster. But more details would help the diagnosis.

#6 8DC

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Posted 21 March 2012 - 05:10 AM

By "long stop" do you mean coasting to a stop? Is it your foot on the brake pedal when the high idle happens? Does the idle drop when you take your foot off the brake, and does it go back up when you press the brake again?

Could be the brake booster. But more details would help the diagnosis.


Car coasting to a stop in neutral, clutch out, brake on. I would have to time it to be sure, but the engine races for a few long seconds before settling down to it's normal idle. It revs up when I put it into neutral and continues for a bit after I come to a complete stop.

It sounds like the BCDD valve, and it's normal to some extent. It's described in the FSM in the Emission Control section.


This revs higher and lasts longer than what I would think is normal. Unfortunately, I can't give specifics on the RPMs as my tach isn't currently working (it's always something, right? lol). I'll break out the multimeter and carb clean this weekend and start chasing leaks.

Edited by 8DC, 21 March 2012 - 05:23 AM.


#7 Backdoorz

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Posted 17 January 2014 - 09:02 PM

I know this topic is old, but decided to add my experience. My air regulator valve was causing the same problem on my 76 280z auto. When I would put it in park, the engine would rev up 4000 to 5000 rpms. Went to the FSM and in suggested 3 possible problems could cause this. The air regulator valve solved the problem for me,






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