Hey guys! Odd cutting out and misfire (electrical or something else?...hmmm)

[Pennyman]

Hey everyone!

1976 280Z, 192XXX mi. (stolen and then recovered...different story haha)

I really didn't want to have to post this, but my beloved Z has been acting strange. While driving, the car will sputter, but won't die. Like it'll hesitate and then come back to live violently, shocking the drivetrain and terrifying any passengers in the car. On the freeway in 5th it's less pronounced because of the gearing, it'll feel like the car is trying to turn off momentarily. So it'll feel smooth and then a small hicup with a loss in power. When the hicup's are more severe I can smell fuel, so it makes me think it's electrical or the plugs getting fouled by oil.

Honestly, I thought it was bad valve guides and burning oil (like I need the top end rebuilt) but new oil hasn't changed it, in fact has seemed to make it worse.

I'm reluctant to say it's the ignition module, but I wouldn't put it past it. I doubt it's the ignition switch itself.

Cap, rotor, spark plugs are new. Oil change 3 days ago. Distributor was replaced about 6 years ago, unknown brand

The car does this seemingly randomly, not related to engine temperature or speed (though it seems more often on the freeway when revs aren't changing much)

Any next-steps or checks I could do would be extremely helpful. Thanks guys

[Pennyman]

Hmm, an update after my drive to work this morning. While warming up, the idle was ok, initial smoky startup. As it was warming up, it would hesitate, and a couple of times it actually died. I would simply turn the key and it would start right up again. It did this a total of 3 times this morning. As you can imagine I was reluctant to drive it to work. Once warm, it seemed to run better.

After it was fully warmed up, I gave it a nice healthy rev, and drove to work, no problems. I'm starting to think the valve seals are toast.

[olzed]

Even if the valve seals are 'toast' that would not be your problem.

If the engine smokes when you accelerate after coasting down hill, can be a sign of valve seals 'toast'

Does the engine use much oil?

[Pennyman]

It does burn oil, quite a bit it seems. I would say a quart or so every 1.5-2 weeks (rotary style). Other than this sputtering it runs really strong.

I'm going to buy a new ignition module (the little rectangular box next to the fuse box) and see if that helps. Little buggers are expensive though...

[Pennyman]

I think I am getting closer to my culprit. I didn't buy the ignition module yet, but while the car was idling, I bumped the sensor wires that are in the thermostat housing. The car faltered and then died, and wouldn't restart because it flooded. I smelled fuel. After cleaning all the spark plugs and spraying some starter fluid in there, it fired up.

I decided to jiggle the wire that I believe goes to the ignition module to switch between advanced and retarded timing based on coolant temperature. Using a ohmmeter, I found that jiggling the wire varied the resistance between 1900ohms, down to 300ohms, and occasionally open (no connection). If this is a thermistor, it should read lower resistance when hot, so the car may be being fooled into thinking the engine is cold, and dumping more fuel in. When the circuit is open, I have no idea what the Ignition module is doing, and is probably confused so it doesn't send anything to the coil.

I guess I'll keep playing with it in the meantime.

[grantf]

Coolant temp sensor and or conections. Sounds like you have found it. My car had the same problem with similar symptoms

[robert84]

I was reluctant to drive it to work. Once warm, it seemed to run better.