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PB Anders - electrical question

Why is it when the lights come on the 914 that the idle fluxuates. Is it an ignition problem or is there a voltage drop to the ECU. Does the 914 need a bigger or better alternator? Should there be a constant voltage supply to the ECU or an isolation circuit that provides plenty of juice to the ECU?
What is it you do for a living Brad? An electrical engineer?
Old 07-07-2005, 02:15 PM
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How much of an idle fluxuation are you talking about? The extra power load on the alternator can pull enough power from the engine to drop the idle a *little.*
Old 07-07-2005, 02:59 PM
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I'm seeing 200+ RPM less than when I have the lights off. Apparently though my car does not like a 500-600 idle. I'm sure the mixture is a little different. Do the injectors not get enough voltage.
I'm hoping PB Anders will chime in with some data or a theory. Then maybe I can measure some component voltages and provide data.

Mike
Old 07-07-2005, 06:08 PM
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altenator...takes HP to make electricity...more load on the alt...the more hp it takes. check for poor connections..
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Old 07-07-2005, 07:26 PM
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I agree but also maybe your idle mix isn't spot on. Adjust it with the engine hot and with a CO meter.
Geoff
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Old 07-08-2005, 07:16 AM
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You probably already know about this page by Brad Anders, but it mentions this:

Q: When I turn on the headlights, my idle drops down to under 500 rpm.
A: Rich idle mixture.
Old 07-08-2005, 01:56 PM
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I have a few things to check now. My CHT sensor reads 1500 ohms at 90F. I'll get a new one tomorrow. I don't think my AAR valve opens or closes so I need to check it. I'll set my idle at 950 RPM and adjust the CO when I complete these tasks. Then I'll report my results.

Mike
Old 07-08-2005, 08:37 PM
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Squirt PB Blaster into the AAR valve to free up the rotary valve inside. (not WD40!)
or you can twist off the top to clean the rust out so it turns freely.
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Old 07-09-2005, 08:18 AM
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I don't think a drop in idle rpm when the headlights are turned on is because of less voltage to the ECU. I believe the rpm drops primarily because the slighly increased current required by the headlights is not sufficiently compensated for by the stock voltage regulator. Therefore, the reduced system voltage to the ignition system does not produce as hot of a spark to the plugs causing the rpm to drop a little.

Phil
Old 07-10-2005, 02:21 PM
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I must have an air leak because the new CHT reads just a little bit higher at 1700 ohms. The car idles better when I unplug the air manifold temp sensor. I hate to dismantle the whole Fi system but I can't find the leak. I did notice I have a bit of smoke coming out of the oil filler tube, that can't be good.

Mike
Old 07-11-2005, 08:14 PM
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