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71 240z high idle


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I'm going to preface this by saying I know pretty much nothing about cars...

I just got my 240z out of storage for the winter -and as I got her only a month before I stored her - I'm not entirely sure if this is a new problem or not.

We had a lot of trouble getting her to start up. One of my friends turned her up higher - my understanding is that this would make her idle higher and start easlier. She only idles at about 1krpm when I start her up. Here's the fun thing: if I'm downshifting for like a stop, she works just fine. If I kick her into neutral, her rpms stay just where they were when I took her out of gear... or even more fun, they go up. So if I'm sitting at a light, she might go up as high as 4krpm. If I turn her off and restart her, she's right back down to a normal idle.

I'm afraid to just turn her down a bit because I'm not convinced she'll still start up fine. Is there some larger underlying problem?

Any suggestions would be great. But I probably won't know what you mean unless you spell it out... LOL Tnx!

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If your car is stock there is a decelleration valve, designed to allow the rpms to drop slowly to help reduce emmissions. When the control valve goes bad sometimes the rpms will hang a little high or not return to idle at all.

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Very stupid question, but if I'm trying to find where that is on my car (looking in my manual) which part of the car would I be looking under to find it? I'm pretty sure that the car is fully stock still, so I wouldn't be surprised if it's never been replaced or even looked at.

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you will see the dashpot and the control valve bolted to the balance tube beween the carbs more toward the front carb. try disconnecting the vacuum line to the dashpot and plug the line then drive the car and see if that helps.

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