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Looking for vacuum leaks and exhaust leaks are a good place to start. If you’ve got any live data at all on your scan tool, look at your fuel trims at idle and then run the car at 1500-2000 rpms for a few seconds. Right now, the fuel trims might be showing corrections in a large positive percentage. When you hit the throttle, the trims should start heading back towards zero. That’s an easy indicator of a vacuum leak. If it’s something as simple as a loose or broken vacuum line somewhere, you might be able to hear it with the hood open. You can shoot soapy water at the intake manifold where it meets the head and listen for the engine to run differently or watch the fuel trims change again on your scan tool. Shoot that soapy water at any point where you think you might find a vacuum leak really. Exhaust leaks in front of or otherwise nearby the upstream O2 sensor can create a false lean condition. Look for obvious holes in the pipe or cracks in the manifold.
If you’ve got a fuel pressure gauge, tap in to the rail and get the fuel pressure with engine running and get a pressure reading with a throttle snap. The fuel pressure should be constant at idle, and on a wide open throttle snap, the pressure should actually go up a little. I don’t have a fuel pressure spec for you. Report your actual fuel pressures if you can though. I’ll make a wild guess that your pressure should be at least in the 40-45 psi range. If you’re below that, you could shot gun a new fuel filter at it without any sort of remorse if it doesn’t solve the problem. It’s a cheap guess and your largest consequence is you’ve got a new fuel filter in the car.
These suggestions don’t cover all the bases, but it’s a good start for now.
Good Luck.
I was looking at other stuff online and I want to know what my Mass Air Flow sensor looks like in the 2.4. Have seen lots on the 3.4 L but they are totally different.
Like no_common_sense stated…no MAF sensor… The 2.4 (Quad 4) engines have a speed-density type of fuel injection system ….no airflow sensor. The ECM uses inputs from the throttle position sensor, manifold absolute pressure sensor, air temperature sensor and engine rpm to estimate airflow and how much fuel the engine needs.
I would follow no_common_sense post above for diagnosis
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