1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Headlights Pull Down Idle, WTF?

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Old 06-19-06, 01:44 PM
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DD Rex

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Headlights Pull Down Idle, WTF?

I've been having a little issue with my Rex. Occassionally, when I come to a stop the car will kind of sputter out. This happens especially right after the choke pops back in. I've been chasing down the problem, idle is set at about 1000 in neutral WITH THE HEADLIGHTS DOWN. I was thinking through this the other day and remembered the idle issue only happened at night or when it rains. So, I tested the lights today, and sure enough, the idle falls from a solid 1000 rpm to about 650-700 rpm with the lights UP.

Are the lights vac operated? Maybe I have a leak? Why would the lights pull the idle down over 300 rpm?

Kev
Old 06-19-06, 02:46 PM
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The lights put an extra strain on the electrical system, causes the alternator to work harder which can slow down your engine. Also, because of the extra pull, theres less power going to your spark plugs which can lower your idle if they arent burning the fuel mixture entirely.
Old 06-19-06, 03:25 PM
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Old 06-19-06, 03:25 PM
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Fresh plugs and plug wires... I wonder if the rotor/coils need looked at. I could also swap to the 2nd gen coil, which I was considering already. This is my DD, just trying to get it running right, especially with all the city driving I do.

Kev
Old 06-19-06, 03:44 PM
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thats an alternator issue. make sure your belt is on good, battery terminals are clean, and if nothing else, look into a 2nd gen alternator. More amps so the alt won't have to strain as hard. good luck.
Old 06-19-06, 03:44 PM
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Check the main power wire that attaches to the positive battery cable. If this is not making a good connection, the alt cannot charge as well as it should.
I had a similar issue, and that was the cause. Of course, it also tended to have the charge meter drop to around 8-10 volts when idling with the lights on. Turning on the turn signal, would cause the tach to jump around in time with the flashing......
Even swapping to a 2nd gen alt didn't help, till I corrected the loose connection.
Old 06-19-06, 03:52 PM
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Try a send gen alt. for extra amps at idle. Also dirty conections can cause abnormal loads in a circuit so you may want to spend a day cleaning your contacts.
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