If you look at your first picture you will see what looks like two wires that have been cut. They are in the wire harness for the EFI. Look just behind the wires that branch off towards the injectors that have yellow tape on them. Looks like cut wires. Thats what it looks like to me anyway.  

Is this not the coolant temp sensor by the starter?

My water temp sensor seems to do fine

Its the one by the starter that's confusing me

And its the stock engine

Never swapped

Just remember seeing these two wires under my passenger side dash

Could these be to the coolant temp sensor

They seem to be the only possible wires

I'm not sure where they lead

They just go into the big mess of wires under the dash

You have all of the puzzle pieces now.  Your stock engine had, and may still have, a coolant temp sensor right next to the water temp sender (for the gauge), in Post #39.  The wires to the sensor would run right next to the wire to the sender.  The sensor might still be there and it might still be connected.

 

If not, you need to find the wires and extend them all the way over to the two white wires connected to the cylinder head temperature sensor (CHTS) in Post #39.  They do the same thing.  That is not the stock head that came with a 1978 car.  

 

Look at the numbers on the head up by the #1 spark plug.  It's probably a P79. 

Yeah it is a p79 head

Haha I was told it was stock

Here's a picture I took long ago of my 76 wires.  Your 78 should be very similar.  Look for wires with bullet connectors.

Okay so my chts is completely disconnected

Yeah I have those

And should probably rewire them

What would a completely disconnected CHTS cause

Yeah I have those

And should probably rewire them

What would a completely disconnected CHTS cause

 

This -

 

 

 

My guess is that for it to run right only when you tighten the living @#$% out of the AFM clock spring, you've probably got an open coolant temp sensor circuit.  Normally when that sensor opens up, the engine will belch black smoke out the tailpipe.  I wouldn't expect the engine to run as well with all the emissions stuff deleted, but I also wouldn't expect it to have this magnitude of problem.

 

Download the factory service manual!    Look on page EF-14.  The big, 2-wire gizmo is the thermotime switch.  The smaller 2-wire gizmo is the CTS for the EFI.  The 1-wire gizmo is the temp sensor for the gauge in the dashboard.

 

This page: http://xenons30.com/reference.html

 

This file: http://xenons30.com/files/FSM/1978%20280z%20FSM.zip

 

Also this file: http://xenons30.com/files/280zfuelinjectionbook.pdf

 

I believe the sensor near the starter would be for oil pressure, but I suppose it could be for oil temperature (a modification someone made).  It's not stock.

Edited June 2, 20159 yr by FastWoman