Won't Restart When Warm

[rmlamp]

I'm new to the 300zx so any input will be greatly appreciated. I have a 1991 2+2 NA that is acting up. The car starts right up when its a cold start and runs well when I drive it. If I shut it down and come back 5 minutes later, it won't start, just turns and turns. If I let it sit for 30-45 minutes, it starts and runs pretty rough for a few seconds and then goes back to running fairly well. I tried replacing the fuel filter and plugs, no change. Another kind of interesting thing it does is if I rev it up to say, 2000 RPM and let off the gas, it will hold 2000 RPM for a couple seconds before returning to idle. I'm at a loss on this one, any help would be great, thanks!

[Jok3r1552]

Check your connections, you could have a bad short somewhere and as far as the RPMs staying consistent with your throttle that you let it go at. Is it at any given time or when its when you start her up?

[rmlamp]

It actually does it worse when it's warm, the RPM can be a bit erratic when its cold too. I'm planning on doing a fuel pressure test and spark test when its warm. I heard the CAS tend to go bad, could it be that?

[nissanfreak12]

Have you checked for ECU codes? Sometimes the check engine light will not flash or illuminate when something is wrong. You need to physically go in and check.

http://www.ttzd.com/tech/diagnostictech.html

My guess would be on the Coolant Temp Sensor could be telling the car it is cold and adding more fuel when it shouldn't be,

Another thought would be the fuel pressure regulator and/or fuel damper.

What style PTU do you have? is it all black? or does it have silver fins in the front(front silver rear black).

[rmlamp]

Have you checked for ECU codes? Sometimes the check engine light will not flash or illuminate when something is wrong. You need to physically go in and check.

http://www.ttzd.com/tech/diagnostictech.html

My guess would be on the Coolant Temp Sensor could be telling the car it is cold and adding more fuel when it shouldn't be,

Another thought would be the fuel pressure regulator and/or fuel damper.

What style PTU do you have? is it all black? or does it have silver fins in the front(front silver rear black).

I haven't tried to pull the codes, I'll take a look tonight. I still need need to check the fuel pressure as well. I heard it could be the coolant sensor but the gauge says its warm, do the gauge and the ecu use the same sensor? I have the old style PTU, it hasn't been relocated, is there a way to test these?

[nissanfreak12]

Well first thing I would do is replace the old style with the new style, these can cause all kinds of problems. Since it was a recall, Nissan should give you a new one. Good luck on that, but they should. It is a recall item, just remind them of that.

The temp gauge is the single wire sensor next to the CTS. The CTS has a square plug on the upper coolant pipe.

[rmlamp]

Well first thing I would do is replace the old style with the new style, these can cause all kinds of problems. Since it was a recall, Nissan should give you a new one. Good luck on that, but they should. It is a recall item, just remind them of that.

The temp gauge is the single wire sensor next to the CTS. The CTS has a square plug on the upper coolant pipe.

ECU threw a coolant sensor code, I just replaced it and it solved the problem. I'll go to a dealership tomorrow and see what I can do on the PTU. Thanks for all the input.