Is this the what I call the sub harness that has the cold start and ECU temp sensor? If so those were available as a unit. Can’t remember where I bought mine but it was the full assembly. Very common to cause ECU issues.

Have you tried cleaning these bullet connectors, tightening them up too?

Is it one of these you are jiggling?

Edited May 10May 10 by siteunseen

1 hour ago, siteunseen said:

Have you tried cleaning these bullet connectors, tightening them up too?

Is it one of these you are jiggling?

I replaced the connectors on the thermotime switch's sub-harness/its oem harness side years ago but left the temp gauge ones as-is and sanded them a bit because they weren't as bad. I'll change the connectors tonight for the temp gauge side regardless, but I don't understand why a higher resistance level/bad connection (which is supposed to richen the engine) caused it to lean out. Basically I'm looking for a definitive thing to point at and say, to quote Al Pacino, "that's the bad guy." Jiggling that wire fixed it, but I don't understand why.

These are the two shakeables in the car that I’ve found so far that cause it to die:

The first is the ecu temp harness connector which somehow even after the car is warmed up leans the engine out further: youtube video here

The second is the main ECU power relay. If you knock on the relay bracket, the engine would die. I took that relay out, cleaned its contacts, tightened the internal screw it has to hold it to its metal cap, then to the relay bracket, now you REALLY have to bang on that bracket to get it to die. youtube video here

This week I learned 'if your engine doesn't run right, jiggle and bang on things'

Edited May 10May 10 by chaseincats

10 minutes ago, chaseincats said:

These are the two shakeables in the car that I’ve found so far that cause it to die:

The first is the ecu temp harness connector which somehow even after the car is warmed up leans the engine out further: youtube video here

The second is the main ECU power relay. If you knock on the relay bracket the engine would die. I took that relay out, cleaned its contacts, tightened the internal screw it has to bolt it to its metal cap then to the relay bracket now you REALLY have to bang on that bracket to get it to die youtube video here

Post driving update: The car drives great - if I had to guess, the bit of dirt/corrosion on the coolant temp wires had the car run in 'fully warmed-up max lean mode' with a car that doesn't get up to 180...but who knows.

My question for you folks is where are you all putting the temp/thermotime bullet connector wires? I popped the hood after driving and these just get cooked in there to the level that the electrical tape glue starts to melt...then will harden again tonight. Granted this is what has been the case forever I guess, but with the new tape/connectors on there, I just noticed it. Is there a place you route them so they get less heat soak or do they just drape over the intake manifold as-is? I used to have them ziptied to the fuel rail but I'm sure that cooked them even more, no?

Edited May 12May 12 by chaseincats

I think I left mine in the same spot but with my header it doesn't get very hot under the hood.

I guess the easiest way would be some type heat reducing reflective tape, heat shield stuff like NASA uses. 😁

41 minutes ago, siteunseen said:

I think I left mine in the same spot but with my header it doesn't get very hot under the hood.

I guess the easiest way would be some type heat reducing reflective tape, heat shield stuff like NASA uses. 😁

Can you post a picture when you get a chance?

https://www.amazon.com/YAMAKATO-Fiberglass-Protection-Automotive-Electrical/dp/B0DZXC2GLH

1/4” should work fine

Edited May 12May 12 by Yarb

5 hours ago, Yarb said:

https://www.amazon.com/YAMAKATO-Fiberglass-Protection-Automotive-Electrical/dp/B0DZXC2GLH

1/4” should work fine

This is a great idea - I’m surprised Datsun didn’t do this out of the gate. Do you use this?

48 minutes ago, chaseincats said:

I’m surprised Datsun didn’t do this out of the gate.

Is your heat shield missing? It bolts on to the bottom of the intake manifold. Blocks heat from the exhaust manifold. Looks like people leave it off sometimes when they install headers.

You can see it here.

https://bringatrailer.com/listing/1976-datsun-280z-39/

Two pieces. One vertical from heat rising, cooking your wires. One horizontal to keep the OE cast iron manifold from baking the TPS and other electrical stuff, BCD and what ever else.