Brief Description:
Car turns over, but won't start. Security light flashing. Replaced coil. Still no spark.

Full Description:
Hi I'm new to these threads. I've searched here and everywhere else online for an answer to my problem but nothing seems similar enough or has given me an answer.
Bought a 1987 Nissan 300zx non turbo 2 seater 5 speed manual with 150k and no cel. Idled a little rough but still ran good, never stalled out or gave me any problems. 3 days later after work I started it, drove it 500 feet, let it run to warm up while I went inside and clocked out. When I came outside it had stalled. When I tried to start it, it sounded healthy and turned over smooth as usual but wouldn't fire. I checked for spark to plugs and while turning the engine over it had no spark, but as soon as I would let off the key it would spark slightly. This happened every time I tried to start it. I let it sit over night with the battery disconnected and the next day reconnected the battery and when I tried to start it she turned over smooth and fired right up. But again after about 3-5 minutes of running it shut off as if I were to turn the key back myself, and again would not start. This time I left the battery connected and the next day it would not start. I checked and there was power to the coil. So I ordered a new coil because I assumed this was the reason I'm not getting proper spark. Left the car sitting for a week with battery connected, coil came in the mail. Today I disconnected battery for about 20 mins while I replaced original coil with new coil, turned engine over and it fired right up. Thought I had fixed the problem. But once again after 3-5 minutes of running it shut itself off and would not start. This time I noticed the orange "SECURITY" dash light was flashing and realized it had been doing this on and off since I purchased the car. I can't figure out if this is and ECU problem, ground connection problem, or a security system problem. Maybe my car thinks I am trying to steal it and the security system disengages the fuel pump? That is what it seems like to me because when the car stalls it doesn't spit and sputter slowly to a stop. As I said before it seems to shut off as if I were to turn the key off myself.

If anyone knows where the root of this issue lies, please let me know. And if you have any other questions, comments, or suggestions feel free to ask. Any help is greatly appreciated. Thanks in advance.

 

Welcome to ZDriver!

First thing, visit XenonZ31 Reference and download a freebie factory service manual - along with all those other cool docs. They will come in handy as you bring your Z back to 100%. Your FSM also is loaded with easy-to-follow inspection and troubleshooting pages. You gotta go through them and set up a time to run the routines laid out and find the issues.

Your stall-out problem sounds definitely temperature-related to me at this point and you can locate the various temp sensors through the diagrams in your FSM. (EF&EC-3 for my '86) They are all important.

Most frequent dead one is your cylinder head temp sensor (CHTS). You can locate it and test it with a multimeter per your FSM. They are cheaper to buy than to get to - but its worth your time. My best guess at this point. If you take the time to get to it, may as well replace it. Aftermarket parts places call it the coolant temp sensor or somesuch. Take the old one with you to compare for fit and connector before you buy.

Just for the hell of it, run a diagnostic (Maybe page EF&EC-35 to begin, then keep reading) at the computer (ECU/ECCS) and see what codes it is throwing at you. The codes are more of a hint than a definite problem item - but they are clues and can help you pinpoint the problem before you throw more unnecessary new parts into the car. Can def be better than blind guessing.

Thanks and welcome again Let's get that '87 on the road again and running perfect! Post some pics for us Z31 freaks.

 

is it a aftermarket alarm ? I would explore it
there were some late 80's alarm systems ( before they were rendered extinct by the key chip) that let the thief take it a block or 2 then shut it off so you do not have to confront him in the driveway. sounds like what you are describing .