Rough Idle

Hello,

It sounds like the fuel pressure is low which will cause the issue. Check fuel pressure with a gauge here is a guide it should be 50-60 psi key on engine off and hold.

Here are two guides to help us fix the problem

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

and

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Please run down these guides and report back.

This sounds like the PCM is seeing the crankshaft sensor fail so it shuts the pump off here is the location of the sensor so you can change it out. Check the diagrams below.

Here is a video of the job being done on you car.

https://youtu.be/sKo7xRWVNqY

CRANKSHAFT POSITION SYSTEM VARIATION LEARN

1. Install a scan tool.
2. Monitor the engine control module (ECM) for DTCs with a scan tool. If other DTCs are set, except DTC P0315, refer to Diagnostic Trouble Code (DTC) List - Vehicle for the applicable DTC that set.
3. Select the crankshaft position (CKP) variation learn procedure with a scan tool.
4. The scan tool instructs you to perform the following:
1. Accelerate to wide open throttle (WOT).
2. Release throttle when fuel cut-off occurs.
3. Observe fuel cut-off for applicable engine.
4. Engine should not accelerate beyond calibrated RPM value.
5. Release throttle immediately if value is exceeded.
6. Block drive wheels.
7. Set parking brake.
8. DO NOT apply brake pedal.
9. Cycle ignition from OFF to ON.
10.Apply and hold brake pedal.
11.Start and idle engine.
12.Turn A/C OFF.
13.Vehicle must remain in Park or Neutral.
14.The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure. The scan tool only displays the condition that inhibits the procedure. The scan tool monitors the following components:
- CKP sensors activity-If there is a CKP sensor condition, refer to the applicable DTC that set.
- Camshaft position (CMP) sensor activity-If there is a CMP sensor condition, refer to the applicable DTC that set.
- Engine coolant temperature (ECT)-If the ECT is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
5. Enable the CKP system variation learn procedure with a scan tool.

6. IMPORTANT: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.

Accelerate to WOT.
7. Release when the fuel cut-off occurs.
8. Test in progress
9. The scan tool displays Learn Status: Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learn procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to DTC P0315. If any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for the applicable DTC that set.
10.Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.
11.The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P0315 is set:
- A CKP sensor replacement
- An engine replacement
- A ECM replacement
- A harmonic balancer replacement
- A crankshaft replacement
- Any engine repairs which disturb the CKP sensor relationship

Check out the diagrams (Below). Please let us know what happens.

The coolant temp sensor may cause temp related issues? You can clean throttle-body and iac/idle air control. Use a gage and check fuel pressure, key on engine off, first thing in the morning.

I want to second JDLs recommendation to test the fuel pressure. This engine is very sensitive to fuel pressure. It requires a minimum of 55 PSI to run.

Look niklis10, If you have a problem with your car, start a question about it but please refrain from giving advice to other people on a subject you have no knowledge in. This is not an 0/2 sensor problem.

Hey, is this a flex-fuel vehicle? If the mil comes on, check the codes. Some of the national brand autostores will check codes for free. Any code you get doesn't tell you what to replace, always check the wiring circuits.

Unmetered air can cause a rough idle, it may seal off after the vehicle warms-up.

First off, I was typing my response at the same time you were posting your last response so I hadn't seen it yet.
We don't address multiple questions or vehicles within the same question and it's very easy for me to see how much knowledge you have by the advice you give. There are professionals here on staff to handle the answers. You stick with the questions. You're only confusing people.

Before you go looking for the hard stuff, charge the battery at a slow rate for an hour with a portable battery charger. Unplug the small connector on the side / rear of the generator, then drive the vehicle to see if the symptoms are different or cleared up.

If things are different, have the charging system tested for maximum full-load output current and "ripple" voltage. If current is exactly one third of what it should be and ripple voltage is high, the generator has a failed diode and will need to be replaced. The third potential symptom of a failed diode is elusive engine running problems. This generator design used by GM starting with 1987 models develops huge, harmful voltage spikes that can damage the internal voltage regulator, short one of the six diodes, and interfere with computer sensor signals. The secret is voltages can be "induced" into sensors' signal wires, and while the resulting voltages the Engine Computer sees are incorrect, they fall within the acceptable range, therefore no diagnostic fault codes are set. About half of the over 2000 potential fault codes will turn on the Check Engine light, so if there's no fault codes, there will be no Check Engine light either. The Engine Computer will accept the false sensor readings and try to run on them.

The most important part of my story is if the generator is found to be developing only one third of its rated maximum current and ripple voltage is high, you must replace the battery and generator at the same time to reduce the high number of repeat failures, ... Unless the battery is less than about two years old. Repeat generator failures on GM vehicles are very common, but it is mainly caused by those voltage spikes they develop, and those spikes are dampened and absorbed by the battery. Batteries lose their ability to do that as they age and the lead flakes off the plates. It might crank the engine just fine, but it's no longer able to absorb those harmful voltage spikes. If you don't replace the battery when this happens, it's common to go through four to six replacement generators in the life of the vehicle.