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HybridZ

hard time keeping her running


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hey guys im having a hard time keeping my Z running, its a 1975 280z. ever since one day when it was really cold she wont stay running unless i keep the throttle open a little, ive checked my EFI and it seems ok and ive look at my plugs and wires and the timing is in and ive checked the seals on the valve cover, injectors, and oil filler cap. im running out of ideas any help would be much appreciated.

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This is in the wrong section, should be under troubleshooting

 

I have a shaved manifold and took my Air regulator off and I have to do the same thing. In the South it wasnt much of a problem as it wasnt that cold ever, but up here in sub 30* weather it does matter.

 

Check your Air Regulator. [it looks like a tube with a coolant line running through it and an injector-style clip on one end]. The connector might be damaged, corroded or loose. If thats OK or you dont feel like replacing it I've come up with a um... 'design' to help with warm ups that lets me keep my idle down so its not idling at 1200 after it's warm.

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Why would you check the alternator?

 

Check your head temp sensor. If that is bad or doing something weird that could also affect the cold idle. The ECU reads data from that, the thermotime switch, and the air temp sensor [located in the AFM] to calculate fuel. Read the EFI Bible. You can find it on a quick search here, it's actually pretty useful. I would recommend spraying the all the connectors with Electric connector cleaner.

 

If the Air Regulator isn't functioning properly, here's what I did for my car:

 

The car isn't getting enough air. If you set the idle higher, you won't need to hold the throttle down. The down side of that is that it idles really high after it's warmed up. I have an unused vacuum hose running through my firewall into the cabin. When the car is cold, I keep it open, which tricks the AFM by giving the motor unmetered air. When the car warms up, I plug it off and the idle drops back down.

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For kicks, remove the breather hose from the valve cover and squirt a little bit of gas down it so it gets into the intake manifold. See if it starts any better when it's cold.

 

The cold start injector may be squirting okay, but may not be staying on long enough to add an real benefit.

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