78 280z idle problem

[Dave WM]

10 hours ago, Jack Pearcy said:

I was getting no reading for the resistance test is why I asked

well there is the problem. So now you have to start tracing, go directly to the sensor try to get a reading from the two terminals. But before you even do that locate the bullet connectors on the sub harness that hooks the sensor to the main harness. Get some pics of that. You could have a bad sensor OR a mixed up connection.

Edited July 1, 2019 by Dave WM

[Jack Pearcy]

okah I’m back. I had 2 weeks of pulling doubles every day and now I’m free again shortly. I got a new CSV and coolant temp sensor, the sensor ended up being the wrong one so I pulled the old one out and cleaned it and put it back in and installed the new CSV and now the car runs well enough to be useable. Now my only issue is the clutch. It still won’t disengage and I adjusted the master cylinder pushrod out as much as I could. I’m beginning to think that the pressure plate may be the problem after all which is unfortunate because that means I’d have to drop the transmission again

[Jack Pearcy]

Here’s the pressure plate I took out next to the one I put in, they look very different

[EuroDat]

It's hard to tell if those two pressure plates are the same height, from those photos. I think the old pressure plate could be higher. I take it didn't come with a new matching collar?

The problem with clutches is over the years there is less and less demand. The industry simply stops making the less demand units, but they forget to include the matching collar so you can use the alternative.

Can you check the position of the clutch fork? Distance from the front of the transmision is a good indicator.

You should measure a distance of about 115mm or a little less. See my post on page 2 #41 for a photo. If the distance is 120mm or more with a new clutch you have a mismatched collar / pressure plate.

You can also try pushing the rod back into the slave cylinder. It should move about 10mm. If you can push it in more than 20mm, not good. Be carefull when you do this. The fluid goes back to the master cylinder and can overfill it.

Edited July 13, 2019 by EuroDat

[Jack Pearcy]

Quick question, which of these would be my coolant temp sensor, I’ve been looking at diagrams and none of them look like what’s depicted or what I got from rockauto. Also the clutch fork is about 4.75 inches or 120.65 mm from the front of the bell housing.

[gwri8]

That green top thing in your hand is a Coolant Temperature Switch/sensor.  The Coolant Temperature Sensor for the temp gauge looks like this and uses the bullet connector.

 

This helps identify the different sensors.

 

 

Edited July 14, 2019 by gwri8
need to clarify

[Dave WM]

the green thing is the "water temp sensor" often mentioned as the CTS, it for the EFI, the single bullet connector item  is the "thermal transmitter", its for the gauge in the dash, nothing to do with the EFI.

I am using the descriptions from the FSM.

The "water temp switch" is a NC switch that opens at about 160f has different functions, on my 75 it controls the EGR activation (EGR not active until the motor warms up). On others it changes distributor timing of the spark module. Perhaps use other places but NOT part of the EFI. You did not picture it but its got TWO leads that come out of it (the only device that has leads) that are terminated with bullet connectors.

there is also a "thermo time switch" This one is both a heater and switch. the switch only closes at temps generally less than about 65f, and when active will only stay closed for about 9 seconds regardless of temps (the internal heater prevents it from staying closed too long). Its function is to add enrichment of fuel for cold starting. Not tied into the ECU its operated solely by the ignition switch. It is the largest of the sensor, mounts on the front of the housing. The sub harness for connecting the CTS and the Thermotime are color coded, but can be interchanged. IF they are not connected properly the EFI will not work as designed. Its important to make sure those two are connected to the right sub harness and that the sub harness bullet leads are connected to the main harness correctly as well. The sub harness has color coded tape near the bullet leads that match the main harness color coded tape. the ends of the harness that plug into the sensors have slightly different colors, perhaps they were more pronounced when new but they are different. I presume they matched with the plastic color of the OE sensors.

 

Edited July 14, 2019 by Dave WM

[Jack Pearcy]

Here’s another angle, it looks like my water temp sensor isn’t connected to anything as you can see the wire with exposed bullet connector just hanging. I don’t see any wires around it that would connect to it but something tells me this might be why I’m running rich. Any idea as to where the wiring to the temp sensor originates?

[Dave WM]

I don't understand that bullet connector. You need better pictures of what is going on.

[gwri8]

The sensor with the bullet connector is the one for the temp gauge. Those sensors mounted in the thermostat housing connect to the harness on top of the intake manifold here.

Here is a little more explanation from the FSM in the EFI section

[Jack Pearcy]

Sorry for the bad pictures it’s hard to get my phone in a position to take anything, here’s some more that will hopefully piece it together 

[gwri8]

You can also check out Blues page for more pictures to help. Just scroll down a little.  http://www.atlanticz.ca/zclub/techtips/electricalconnections/index.html

240260280  is the author of that site and it covers everything.  A great resource for Z owners.