Engine dies for 10 seconds, pops back on.

[Afrikaaner]

Hey, my 90 NA z is giving me issues... It's right before I start my tt swap, so I'm not TOO concerned, but I'd love to figure this out before I put another engine in it. The first time this happened, I was sitting at a light, and my engine conked out. Slightly concerned, thinking perhaps my alternator died, I turned the key, expecting it not to turn over, but in fact it did. And it turned over and over and over, and nothing. Rolling forward down the hill a little (the light turned green), I tried pop starting it, but it wouldn't start. I pulled to the side, cursing a bit, and then tried the key again, this time stumbling to life, but once i gave it a little gas, it was fine. The same thing happened again at a different light later that day. For a few days I thought maybe it was nothing (while knowing that on a z, it's never nothing), but then two days ago on my way to a buddy's house, while I was driving, the engine died again, while in gear driving maybe 40/45 mph. The car was still in gear, so I was just slowing down. I think I just left it in gear, wondering what I should do, when it kicked back on again. The only thing I could think of was possibly the fuel pump is getting old and lazy? The car has over 120k on it, and I know it has about infinity electronic systems that cause horribly odd things like this to happen. Also, every time the car died, it was warm, on the verge of hot, but not 100% hot yet. Your thoughts?

[Ace2cool]

Now when you say "on the verge of hot", how hot are we talking? Could be the ECU shutting the engine off due to an overheat condition.

[Afrikaaner]

by hot, i mean fully warmed up. i don't know about everyone else's z32, but mine takes a LOONG time to get to it's peak temperature (judging based on the air coming out of the vents in winter). My temp gauge just goes to the middle very fast, and then sits there even if the car isn't totally warm. AND i drained some coolant (which I replaced, but perhaps there were bubbles?), so I'll double check my coolant levels when i get home. another person i was talking to mentioned the possibility of a short, though i think that seems a little unlikely to unshort itself so fast.

[Ace2cool]

Sounds like a MAF issue to me. I've had the MAF cause my car to shut off on a previous, very similarly designed vehicle, and not start back up until the key was turned fully to the "off" position, and tried to start it again. Happened like exactly what you're describing.

[Afrikaaner]

hmmm interesting, does the fsm tell us how to test the maf?

also, i took it out for a drive yesterday to see what the symptoms are more clearly, and it died almost every time i would stop the car and put it in neutral. the obnoxious thing was that once i parked it at home, it idled just fine. back to the issue though, the car would come down to idle, then stumble a bit around 5 or 6 hundred rpm, and then rather suddenly die. my idle normally hunts up and down a bit usually between 600 and 900 rpm, but it drops to 500 now and again, but used to recover from this. it also died while running once for maybe 2 seconds, and then it kicked back on. probably would be worth pulling codes...

but honestly, i'm thinking more and more that this is related to the wiring harness. there have been other issues with it in the past and i had to rewire cylinder 5's coil pack because there was a short or break in it that was causing the coil to explode. so perhaps the best thing to do would be get the engine swap done (which would include a new harness) and then see if the problem presents itself again? what do you guys think?

[Ace2cool]

I still think it's the MAF. There is a testing method. Let me see if I can find it.

EDIT: I take that back. There's no test in the FSM for the MAF. However, there's an easy, sure-fire way to tell it it's your MAF. The eesist way to tell if it's your MAF is to take the nose panel off, start the car, and let it warm to operating temperature. Then, take a screwdriver handle and tap it. If the engine stalls, that's your problem. That's how I troubleshot my old SVX. Every time I would tap the MAF, it would die. Your MAF should hold idle when you tap it.

[Afrikaaner]

well i was going to try your tap the maf trick, but now the car wont even start. i am going to test for spark once i have a buddy come by, but for now, it's out of commission.

[Ace2cool]

Sorry to hear man. Question: When you turn the key to the "on" position, do you hear the fuel pump priming in the back? When was the last time you changed the fuel filter?

If those things check out, next step is spark.

If you have fuel, spark, proper timing, and air, the engine will run, almost guaranteed. If it doesn't, something else is amiss. Good luck on tracking the issue down, bro.