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Hi. First of all, I'm new to this forum and I'm new to Nissans. I just bought a '85 300ZX non-turbo 2+2 about 6 weeks ago and it appears to have developed some electrical issues which I'm hoping are related (possibly via a bad ground), but I don't know where to look. This is the digital dash version. When I bought the car, the ambient/set temp display was dim in the daytime but it disappears completely at night when the lights are on. The previous owner told me about this and I figured I could just ignore it. Then I noticed a lot of ignition noise in the radio and figured on going in and finding the ground or creating a new one. I don't listen to the radio and the tape deck is broken so I figure I can ignore this for a while too. This is the radio with the graphic equalizer. Now here's the real question that's bugging be. Last weekend I noticed the idle was high. The car was idling at anywhere from 1000 to 1200 rpm after it was warmed up. I adjusted it down to 700 and everything was ok until it was cold the next morning when it still ran at 700. Seems to me it should have run higher until it warmed up. Now I'm noticing that any kind of electrical load will increase the idle speed proportional to the size of the load. Turning on the headlights ups the idle to 900 rpm. The defroster is good for 1000 rpm or more.depending on if it is on defrost or demist. When this happens I can unplug the up idle solenoid and the idle will drop back down to 700 rpm. Any ideas? The idle issue is the only one I can't live with but I'm wondering if all these might be related somehow. It looks to me like some bad voltages are getting to the up idle solenoid but looks can be decieving. Please help. Thanks.
 

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i also have an 85 z only turbo n have had similar problems electrically and its seems 2 b gettin worse ive gone through 3 computers in the past 2 months i have the same idle problem also if it progress's n gets worse it might b sumwhere in the wiring harness or as u said a ground im not sure im also trying 2 c wuts wrong with mine so if ne1 else has ne suggestions as to why i cud be going through computers that quick that would be great i cud use all the help because no i have start rebuildin it cuz my mechanic screwed it up bad wit the intent of me getting rid of it so he cud take but i wont give it up that easy

so ne suggestions thx
 

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Sounds like both of you guys are experiencing grounding problems. Bad/intermitent ECU grounds will fry an ECU in short order. There are a few grounding points on the firewall. You may also wish to make sure the motor grounds are in place and clean.
 

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To second that, a really good idea is to replace the motor, alternator, battery etc etc grounds that are 20 years old with seperate wires that will mock the hyper ground systems that are so popular now, you can easily do it yourself with 10 or 8 gauge wire and good connectors. Ground everything back to the battery and then use a 0 gauge directly to the frame in the shortest distance possible, that may help alot.
 
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