Cold engine problems

[feydjm]

Greetings everyone,

My 85 NA 300ZX has a problem when it's cold. I don't mean like december cold, just normal in the morning cold. First it doesn't want to catch and fire when starting. It turns over like it wants to catch, but just takes a while to do it.

Once it starts it runs really rough until it warms up. Once it's warm it runs fine, but until then it rough. Hard to accelerate, rough idle, etc. Sometimes, if I can get the RPMs up, I can push through it, but mostly I just deal with it until it gets warm.

I've done:
Cap and rotor
New Plugs
New Fuel Filter
Checked timing

I've replaced some old vacuum hoses and have a Cone filter for the intake.

Thoughts?
Justin

[k3smostwanted]

Originally Posted by feydjm

Greetings everyone,

My 85 NA 300ZX has a problem when it's cold. I don't mean like december cold, just normal in the morning cold. First it doesn't want to catch and fire when starting. It turns over like it wants to catch, but just takes a while to do it.

Once it starts it runs really rough until it warms up. Once it's warm it runs fine, but until then it rough. Hard to accelerate, rough idle, etc. Sometimes, if I can get the RPMs up, I can push through it, but mostly I just deal with it until it gets warm.

I've done:
Cap and rotor
New Plugs
New Fuel Filter
Checked timing

I've replaced some old vacuum hoses and have a Cone filter for the intake.

Thoughts?
Justin

Low compression or Idle Air Control Valve. the IACV has a sensor in it for cold starts that richens the air/fuel.

[Andrewhuffman]

+1 for the IACV

[DeleriousZ]

First of all, run the ecu error codes via this procedure and see what comes up.

The CHTS can cause a ton of cold-running issues, but the early ECU's also have a cold stumble issue that hasn't been solved yet. If that's the case you'll either have to deal with it or find a newer ecu that's set up for the correct o2 sensor and injectors for your car.