Strange Power and Accessory Problem

[kboyd92]

Hello! Im hoping someone can help me sort out this headache. I have a 1992 NA 300zx, manual, stock ECU, and no deletes, 108k miles. This is my second Z purchased as a daily. My boyfriend and I also have another 1992 NA in the middle of getting a TT swap. This car has become a donor car for the daily as we work out a few issues. The daily was running perfectly until about a week ago.

Some background on recent issues (maybe related to the current problem?): The car was trying to shut off when braking hard or turning corners at high speeds. It is also running rich and has a slight misfire. One day it died at idle when coming to a stop. The car then wouldnt start. Turned out the signal wire to the starter had unsoldered itself from the starter. We swapped the starter from the donor car to the daily and the car started up without hesitation.

However, now there is an intermittent loss in power to the accessories and it seems like it wants to die at idle. There was a very loud buzzing behind the dash on the drivers side that turned out to be a relay. We replaced that and the buzzing went away but the power is still dropping and surging. Some days it runs like a champ....other days the headlights, radio, and accessories all cut in and out losing power. We had the battery and alternator tested on a good day and everything was functioning properly. We then had them both tested on a bad day and the alternator reading would drop. There is also resistance in the ground wire by the battery. There was a vaccum leak causing most of the idle problems so we repaired that. Idle still fluctuates. Once the car reaches higher rpms it runs like a champ.

The IACV, TPS, EGR, Coolant temp sensor, Engine temp sensor, just about everything has been switched over from the donor car in attempt to track down the idle problem. The donor car ran perfect before doing the swap. Most of the parts swapped were brand new.

This is a very intermittent problem. As mentioned earlier the car will run perfect on a good day with zero surging or idle problems. 50% of the time we will have issues. Im not as educated with the Zs as my boyfriend is but I am trying to learn before he loses motivation and decides to hold off on the TT swap. Any insight would be greatly appreciated.

[centralcoaster33]

Sounds like wiring/ relay/ or switch problems. Did you swap over the ignition switch? That has the connections that turn accessories 1 and 2 on and off as you start the car or have it on or whatever. I'd get the FSM and look at the EC chapter for diagrams and diagnoses. What relay was 'buzzing'? The "service manuals" link at the top of the page should get you there. You can download the PDF's so you can view them when you're offline.

Welcome to NICO!