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Y'all are my last hope. Car idle is rough when car is warm. Pressing the accelerator the car stutters and the rpm guage jumps a bit. Have replaced plugs, wires, o2 sensor, fuel filter, maf sensor, and cleaned the throttle body. The check engine light IS NOT on. Don't know what else to do. Thanks!!!
 

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Several things that could cause your problem:

* This is one of the most common ones. There may be a major intake system vacuum leak. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be around 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.

* Incorrect fuel pressure. Tee-in a temporary fuel pressure gauge between the fuel feed hose and the fuel rail. The readings at idle should be as follows:
  • with vacuum hose connected to the fuel pressure regulator: 34 psi.
  • with vacuum hose disconnected from the fuel pressure regulator: 43 psi.

* What brand of spark plugs are you using? You should be using OEM NGK plugs; other brands such as Champion or Bosch many times cause driveability problems in Nissan engines.

* Dirty fuel injector(s). Run some good injection cleaner, like BG products 44K, through the system; give the cleaner about a week or two to do it's job.
 
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