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Help: engine does not keep idle unless key turned


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This could be a unique problem, not sure tho

 

so here's the issue: one day it stopped working like it should, one day it was working fine, we removed the air conditioning unit, and the next it refuses to hold idle.

 

What happens is when you turn the key, the engine runs and revs fine, but when you let go of the key, it dies instantly. So obviously starter is fine, and we think the carbs are fine too, but we can't figure out for the life of us what is wrong. The air filter is off fyi. Vacuum advance is disconnected.

 

Compression is real good so this is quite confusing for me and my cousin.

 

We were considering doing a four-barrel conversion but we're not sure how much that is going to help our situation.

 

please help!!!!!

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I had exactly the same problem a few years ago only mine quit running while doing 65 down the freeway. It turned out that my ballast resistor on the coil had gone bad. It would start and run with the key in the start position because the ignition switch on the original equipment bypasses the voltage drop to the distributor to increase spark power during start-up. Worth a check...

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on older Z's the coil ran a lower voltage than 12v for Starting though, it would run on 12v. the ballast resistor would drop the voltage while running. When you're starting the car though, the resistor is bypassed. if the resistor is shot, then when you let go of the key from START to RUN the coil's voltage gets cut off totally. it's not a part of the coil, but hooked inline on a wire.

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On a stock series one Z the balast resistor is mounted under the coil on the inside drivers fender in front of the shock tower (USA versions). It looks SIMILAR, not exactly, like the one in the picture. The easiest way to check is with a test light. You can get one from Kragen or Napa for under $10 and it will help in the rest of your wiring problems. It looks like an ice pick with a cord out the back and a light bulb inside. Turn your key to the on position. Clip the test light to ground like the bolt that holds down the coil or the resistor. Touch both sides of the resistor terminals one at a time. The light should come on for both sides but one side should be dimmer than the other. If both sides don't light you are doing something wrong. If one side does not light, the resistor is bad and needs replacing. If both sides light, your problem is somewhere else and you should go with the ignition switch idea.

 

Try this link for what a test light is http://www.partsamerica.com/productdetail.aspx?MfrCode=DOR&MfrPartNumber=86598&CategoryCode=3391

 

Good luck.

 

Paul

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