Cold Start Issues - Engine sputter (77 280z Auto)

[S30Driver]

The cold start injector only operates for a very short time when motor is first started.  I doubt it is causing the idle issue when cold.

You can test it by removing it and tape or plug the intake manifold where it mounts, put valve in a container & start motor.  since you replaced it, it is not likely leaking fuel after startup.

The reference to the brass connectors, I believe is a reference to the electrical connectors on the wiring harness & sensors.

[siteunseen]

10 minutes ago, MH77280Z said:

We installed a new Standard Motors cold start valve. I can clean the bullet connectors but what does that mean? do u suspect the injector is not working due to corroded connections etc.?

You can pull it and it put in a glass container and see how much it fills. Like s30driver says it only comes in at start up but they do leak when their bad adding fuel. They're on the same 30lb something high pressure side of the pump. On cleaning the bullet connections I say shine up all connections. It won't take long and cost nothing.

Here's the main thought on shing up old connections.

https://www.atlanticz.ca/zclub/techtips/electricalconnections/index.html

[Dave WM]

any time you have a cold running issue that goes away at warm up you need to check the water temp sensor resistance while the engine is cold AT THE 35 PIN CONNECTOR.

read the fsm on what you should see. perhaps you have already done this.

[MH77280Z]

1 hour ago, Dave WM said:

any time you have a cold running issue that goes away at warm up you need to check the water temp sensor resistance while the engine is cold AT THE 35 PIN CONNECTOR.

read the fsm on what you should see. perhaps you have already done this.

When u say 35 pin connector - where is that? Appreciate everyone’s patience 🙂

[Yarb]

At the ECU.

[MH77280Z]

6 hours ago, Yarb said:

At the ECU.

Ok let me measure that and also clean the bullet connectors and brass contacts on all these sensors like others also mentioned.

[MH77280Z]

18 hours ago, Dave WM said:

any time you have a cold running issue that goes away at warm up you need to check the water temp sensor resistance while the engine is cold AT THE 35 PIN CONNECTOR.

read the fsm on what you should see. perhaps you have already done this.

@Dave WM I looked at the diagram and the pins labeled on the water temp sensor are 13 and 49 I believe. What is a 35 pin connector?

[Dave WM]

the large connector that attaches to the ECU. refer to the FSM for the pins to check see the fuel injection section. there is a diagram that you can follow.

[Yarb]

Make sure of the orientation of pin numbers so your not getting false readings. Its easy to do.

[MH77280Z]

There is one more observation today ...

I cranked the car cold and rpms were abrupt and i had to keep the paddle pumping to keep it alive and sometimes it went to high RPM (as expected) but within 1 min of running and sputtering like this it suddenly smoothed out. I am very sure the engine was NOT at operating temperature. So something got corrected during that 1 min...

Dont hate me for it guys ... what do you think?

 

[Zed Head]

Kind of sounds like the bad ECU problem, or bad ignition module.  Did it smell like raw fuel?

 

 

[Yarb]

My recommendation is to go back to the EFI section of the AFM. Start at the beginning and work your way through it recording every reading you get with your meter. Make notes and work through it. Chances are it’s multiple issues you are dealing with. There’s not a simple answer for these antiquated EFI cars. The more you check the more you will learn what makes the system tick. A lot of patience. Wish I had a better answer for you.