Getting clouds of smoke and very inconsistent idle speeds - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 7 (permalink) Old 09-22-2019, 11:02 AM Thread Starter
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Getting clouds of smoke and very inconsistent idle speeds

I have a 1980 Datsun 280zx and I finally got it to start I donít know how was just tinkering and poof. It was idling super low and I tried to gas it in neutral to see if I could get it to take. It didnít rev up maybe a little but not enough for it actually sound like it. I got out and there was a giant cloud of smoke that had no recognizable smell to it. Then I went back through and took out a couple spark plugs and looked at them went to do it again and it fired up but idled crazy high and my fan seemed like it was running overtime. When I gassed it just a tiny bit definitely didnít come down as fast as it should and went way to high up for the amount of gas I gave it. I believe it to be electrical issues but very well could be wrong. Do fuel injectors commonly go out on these Zís? In the past it has started and then died and had a rough idle until I drive about a quarter mile. Iím worried about a head gasket so I wonít be driving it more than around my driveway once today to see what happens. Iím new to the car world and will fully Search any suggestions you have and answer any questions you have. Thank you!
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post #2 of 7 (permalink) Old 09-22-2019, 11:57 AM
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down load the FSM for you model and read the fuel injection chapter. There is a complete section devoted to cause and effects. You did not give much useful info to make a diagnostic on it. Example, you pulled the plugs and did not described the condition (rich/lean) at a minimum you should post pictures of the plugs or better yet a video of the problem. If its running rich its likely a problem with the temp sensor. Cloud of smoke could be fuel/oil/water, each have there own issue. at a minimum you will want a fuel pressure reading and some base line timing readings.
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post #3 of 7 (permalink) Old 09-22-2019, 02:26 PM
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Normally...

Water smoke is white
Oil smoke is blue
Gas (rich) is grey

I agree, the description is jumbled and needs to be a bit more methodical. Breaking it up into specific symptoms helps.

IIRC you could not get it started earlier. What happened to make it run? Whatever you were fiddling with evidently made a difference.

How old is the gas? You may be running some bad stuff through there, and that may obstruct injectors.

Idling "super low" isn't enough detail; what RPM is the tach showing? 600-700 is OK for my 280ZX.

Last edited by pilgrim; 09-22-2019 at 05:17 PM.
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post #4 of 7 (permalink) Old 09-22-2019, 05:17 PM Thread Starter
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Sorry I’m 16 and type like a 16 year old too. I was messing with the spark plugs and looking at fuses. I also did not know that you can post pictures on here. I believe it’s running rich. I just drove it and had to have the gas pedal pinned because it was not responsive and then when I tried to down shift into first gear it would rev up very high. I checked my throttle cable and it had a lot of slack in it and my gas pedal felt stuck down. No smoke this time. I’m going to read more of the fsm and see what I can troubleshoot thank you all again!
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post #5 of 7 (permalink) Old 09-22-2019, 05:19 PM Thread Starter
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Gas is not old at all and I put fuel injector cleaner in it right before it acted up
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post #6 of 7 (permalink) Old 09-22-2019, 05:30 PM
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Good that there's no smoke.

When you shift down, does it idle at high RPM *before* you engage first gear? This is probably too obvious to point out, but on a downshift it's normal for the RPM to rise when first gear is engaged.

It sounds like when you de-clutch, the RPM rises; if so, I would expect that to happen between all gears (please confirm) but to what RPM does it rise?
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post #7 of 7 (permalink) Old 09-22-2019, 05:58 PM Thread Starter
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I donít have an rpm gauge but I do have a loud exhaust on there. When I drove it I engaged the clutch and the rpms shot up when the clutch was engaged definitely enough for me to notice. But then after putting in in first it would only crawl forwards.
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