Really hard electrical problem

[Zed Head]

The brake light will come on when engine RPM drop so low that the alternator isn't charging.  So that might be a non-issue.  Sounds like your engine just stops running well, almost like it's running out of fuel.  Could be blockage in the fuel tank.  If you can hook up a fuel pressure gauge and put it somewhere that you can see it while driving, you'll know more.

[Xenn]

Actually my car idles below the alternator charge point (600 for idle, 800 when the alt kicks in) I can tell because of the volt meter and the sound of the fuel pump, brake light comes on below about 3-400RPM. But you are right, its a non issue.

I had the same thought about the tank, awhile ago when i was sorting out this problem. I replaced the fuel pump, bypassed the fuel damper, and blew the lines out with compressed air both ways and back into the tank, then installed an inline filter before the pump, there might still be some flake of something in the tank that likes to cover the hole though. I installed an inline fuel pressure gauge between the cold start injecter and rail just to check that, but it was cheap and broke already, I need to get a new one before i can check it, however the fuel pump does not sound different when dead. Problems usually happen at about a half tank or less though so maybe still.

I recleaned all my engine bay grounds, and went a step further and did things like cleaned the metal contact where the bracket the ECU grounds to, connects to the intake manifold, the car sounds great again, a slow decay is hard to notice, mostly i notice in how eaisly it starts up now again but who knows how long i need to wait to see if it dies again.

Its kinda sad the best running Z ive had likes to die randomly haha.

Thanks for all your help Zed Head, im starting to feel like i have picked you guys clean for ideas now though.

[Zed Head]

No problem.  Good luck.  Make sure that the distributor body has a good ground connection.  The module and coil current passes through it.

[Xenn]

A quick question, i hear tell of grounds by the ECU and fusebox, does anyone have a pic of these, i have never found them.

[Xenn]

So, a new piece of information. This morning on my way to work a semi pulled out in front of me on the sheet of ice we call a highway, i slammed on the brakes and horn and pulled off the road to not hit him (canadian driver) while i was doing this I noticed the horn was going in and out and i could hear clicking by the fusebox, once stopped i realized my car was doing its unwilling to run thing again, making me think I have a loose wire or dieing relay by the fusebox that is causing my problems, any suggestions as to where/what to look for when i go digging later? I know the wiring under there is a little shot, the previous owner did a headlight relay harness upgrade and bypassed the fuel pump relay, as well as installed a car alarm (which i have now removed BTW).

[Mark Maras]

 No meter repair. Hook up a temporary ground to any "suspect" ground circuit using a length of wire and two alligator clips to see if "things" improve. If that perks things up, add a semi-permanent ground to the circuit until the orig. fault can be found.

[Xenn]

On 12/15/2016 at 1:13 PM, Mark Maras said:

 No meter repair. Hook up a temporary ground to any "suspect" ground circuit using a length of wire and two alligator clips to see if "things" improve. If that perks things up, add a semi-permanent ground to the circuit until the orig. fault can be found.

Good idea, ill try that.

[Zed Head]

The  horn and the clicking relay just sound like low voltage being supplied, probably because the engine was about to die while you were laying on the horn with the brakes applied.  I had a similar problem when I was getting my engine parts all back to good working order.  Used to happen when the engine was cold as I approached the first stop sign out of my neighborhood.  Turn up your idle speed and adjust the dash pot so that when you let the throttle pedal up the engine speed doesn't drop so fast.

[Xenn]

Positive update, i went digging through the electrical rats nest that the previous owner turned the wiring by the fuse box into, when I found out that when I moved the harness, i could hear the fuel pump waivering, i chased the connection back to where the FP ties in, and they had used a funky connecter where you strip the end of one wire, the middle of a live line, set them next to eachother, then fold a strip of metal across them both, and its all encased in a little box which I had previously thought was a fuse or resister. So i tore that out and properly sodered it, as well as all the other wires that had been connected like that, and one with a small twist connection that was coming apart, suddenly the fuel pump does not waver when moving the harness, and my turn signals work again.

I have no idea which systems I effected while under there, however my car has had no running issues since then (though it has only been a short time so far), I hope it serves as a warning to those to always properly wire electrical systems, with solder, because it can cause nightmare to diagnose intermittent failures for you later on, or the next poor person who has the car.

Edited December 21, 2016 by Xenn

[Xenn]

It came back after like 2 weeks of running great, im running out of ideas, the fact that it will suddenly run fine for weeks or months then just crap again out i cant explain.

[Zed Head]

Take a shot at describing exactly what happens again.  It might help you understand the problem and will give people out here better clues.  The whole thread is kind of vague - "really hard", "crap out", etc.  Just trying to think of the right words to use will make things clearer for you.

[Xenn]

Well for instance this morning, I was driving to work, coming up on a stop sign, put the car in neutral started to slow down, realized my brake light was on, looked at my tach and it read 0, sat at the light with my car off until it turned green, at which point i was able to start the car no problem, drove down the block and right as i was pulling into a spot to park my car, it died again, testing it i can hear the fuel pump going, but it wont fire when it turns over, waiting 1 minute it will start but while running it sounds like the engine wants to die, such as it runs fine, then it sounds like someone kills the power for a split second, rpms drop a few hundred from idle and car nearly dies then catches itself, it does this once or twice before finally turning off. Waiting 5 minutes the car will start fine and be driveable for long periods. Sometimes there is variation on this, but as i keep working on my car the symptoms become less when it acts up.
It will seem to run fine for weeks, act up for a few days then be fine again. I have replaced the: distributor (and ignition relay) , ignition coil, ECU, temp switches in thermostat, fuseable links, alternator (and voltage reg), fixed and cleaned all grounds, removed the aftermarket alarm, repaired a bunch of wiring to the fusebox, replaced fuelpump, injectors, pressure regulator, and filter, AFM, and probably a few other things i cant think of.