mrdark

'81 280ZX N/T

So, every morning, this is what the car does when started. It'll crank over and start the first time, but stall immediately. Try two is the same results, but it doesn't die as quickly. Try three or four, I can feather the gas pedal, to keep it from stalling, then pump it until it gets past 2k RPM, and it will idle, but roughly. There's usually a backfire in there somewhere.

It will fall on it's face if you try to drive it immediately, unless you let it run for a few minutes. Past then, it's sluggish and falls on it's face until normal operating temperature.

Things I've done-

• New cap, rotor, plugs (gap is correct)
• New ignition coil and plug wires
• New PCV
• New fuel pressure regulator
• Did the AFM rebuild
• Confirmed proper TPS operation
• New fuel filter and checked fuel lines

Observations-

• Plugs look normal
• Generally sluggish acceleration under 30MPH
• Injector cooler does not typically run with daily driving
• Injector cooler will run after moderate engine racing and remain running after shutting off car

It has good pull past 30MPH when warmed up. I'm starting to suspect a sensor of some sort. Or the cold start valve?

Has anyone had a similar problem?

iamericgee

so what's the problem ? lol

NismoPick

If the problem is temperture related, you need to check the items related to temperture:
-CHTS
-Air Regulator
-Cold Start Valve
-Air Intake Temp (white node on the AFM intake)

Also,
What is the timing at?
What is the fuel pressure?
What specifically did you do to the AFM?

The injector fan kicks on when the coolant temp gets above something like 220*F at any time during that run (check the Haynes / FSM for the exact temp). So is the temp gauge going over half way?

ThaPimpShrimp

I'd definitely check the functionality of your cold start valve! Though it sounds like may not be your only problem.

mrdark

Okay, so the fact that the injector cooler comes on indicates that the coolant temp sensor is most likely working correctly then, that's good.

I'm pretty sure fuel pressure is normal, but I'm going throw a gauge on it this weekend as well as check the timing. Failing that I'll run through the other components you listed.

The AFM was actually pretty clean when I pulled it out, it had a reman sticker on it, so it was done at some point. I moved the circuit board slightly per the post in this forum, so it had new carbon track to run on. Sealed it back up and put it back in. It seemed to improve throttle response but that could have been a placebo effect. So I'd say minimal to no change there.

Anyways thanks for the info, it's a good starting point. I'll let ya'll know what I find.

FricFrac

The injector cooler fan has its own thermal timer switch IIRC. It's it's own system.

For the AFM make sure you've got a good electrical connection. Meter it out as per the FSM and make sure it's in spec that way.

flores21

ya cold start valve should definitely be checked mine is wore out as well and it runs like crap when its winter time, either that or check but the bad idle and falling on its face which mine was doing for the past few days was because of a bad for, maybe fuel pump?

mrdark

Follow-up to this post. It was a combination of a shady connection to the cold start injector, and the air regulator was no good. If you suspect your air regulator, go pull it off the car on a cold morning, and see if the door is open or closed. If it's closed, it's likely faulty, as was my case. With the new air regulator the car will start around 1500 RPM and work it's way down to normal in about a minute or so.

Make sure to clean your wiring to the thermotime switch and the cold start injector.