Is the check engine light staying on when the engine is running? If so, have the computer scanned to retrieve diagnostic trouble codes. Here is a quick video showing how it is done:
I realize not everyone owns a scanner, but most parts stores will check it free of charge.
Next, in most cases, an oxygen sensor will set a code, which till turn the check engine light on. If that isn't the case, my next suspect is either an engine vacuum leak (when it's cold, steel contracts), or there is a problem with the engine coolant temp sensor (ECT). The ect is responsible for telling the computer how cold the coolant is. With that info, the computer determines how rich or lean to make the air / fuel mixture. If it thinks it's warmer than it is or opposite, that will cause a rough idle or even worse.
Now, this sensor may or may not set a code, because as long as it is sending a signal, the computer doesn't know if it is correct. The easiest way to check it is with a live data scanner. When the engine is cold, plug in the scanner and see what temperature the sensor is indicating. It should be very close to the outside temp.
I attached two pics below to show location of the sensor. If you can't get your hands on a scanner, here are the specs which the sensor should meet based on different temps. Basically, you have to check resistance.
Temperature C ( F) Resistance k ohm
20 (68) 2.1 - 2.9
50 (122) 0.68 - 1.00
90 (194) 0.236 - 0.260
You will need a multi meter to do this. Here is a link that explains how to use one:
Next, I would suggest checking for an engine vacuum leak if everything else checks good. Here is a link that explains how it is done:
One last thing is fuel pressure. Since the engine requires more fuel when it is cold, weak pressure can cause an issue as well. Here is a link that shows in general how to test fuel pressure:
Here are the specific directions and specifications for your vehicle.
2000 Nissan-Datsun Maxima GLE V6-3.0L (VQ30DE)
Component Tests and General Diagnostics
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Testing and Inspection Component Tests and General Diagnostics
COMPONENT TESTS AND GENERAL DIAGNOSTICS
- When reconnecting fuel line, always use new clamps.
- Make sure that clamp screw does not contact adjacent parts.
- Use a torque driver to tighten clamps.
- Use Pressure Gauge to check fuel pressure.
- Do not perform fuel pressure check with system operating. Fuel pressure gauge may indicate false readings.
1. Release fuel pressure to zero.
2. Disconnect fuel tube joint in fuel line and set fuel pressure check adapter (J44321).
3. Install pressure gauge to the fuel pressure check adapter as shown in the figure.
4. Start engine and check for fuel leakage.
5. Read the indication of fuel pressure gauge.
With vacuum hose connected Approximately 235 kPa (2.4 kg/sq.cm, 34 psi)
With vacuum hose disconnected Approximately 294 kPa (3.0 kg/sq.cm, 43 psi)
If results are unsatisfactory, perform Fuel Pressure Regulator Check.
I know this seems like a lot, but if there are no trouble codes, it becomes a process of elimination to determine which system is causing the issue.
Let me know if this helps or if you have other questions.
Images (Click to enlarge)
Thursday, January 23rd, 2020 AT 7:46 PM