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2002 Pontiac GPX 3.8L Troubleshooting: P0172, P0101, and P0103 Fault Codes - Rough Idle, Stalling Issues

Model: 2002 Pontiac GPX Fault Code: P0101 Posted: 2009-02-16 14:30

Hello, I'm experiencing persistent rough starting, rough idle, and stalling problems with my 2002 Pontiac GPX 3.8L. After reviewing the P0172 diagnostic information, I've been systematically replacing components to resolve these issues. Two weeks ago, I received MAP sensor fault codes (P0101 and P0103). I replaced the Mass Air Flow (MAF) sensor first. While this improved performance slightly, a stalling issue remained. I then replaced the idle control valve, PCV valve, cleaned my K&N air filter, and performed a throttle body cleaning. The car ran smoothly for about two weeks. However, on Saturday, while stopped at a traffic light, when I pressed the XLR8R pedal to accelerate, the engine stalled again. Based on P0172 symptoms (rich mixture due to air flow or sensor issues), I'm now planning to install a dry air filter and use electrical cleaner as recommended. However, I'd appreciate any additional insights from other owners of this model. Could vacuum leaks be contributing? Are there specific sensors or components commonly failing in 3.8L Pontiac GPX engines with these codes? Thanks for your help.

Related fault codes
P0101P0103P0172
Comments (5)
Anonymous 2009-02-17 06:46

Vacuum leaks are a common cause of P0172, P0101, and P0103 in the 2002 Pontiac GPX. Carefully inspect all vacuum hoses—there are only a few—and replace any cracked or disconnected ones. This is a relatively simple and inexpensive fix.

Anonymous 2009-02-17 07:12

I'll reinspect the vacuum lines again, especially after reassembly a couple weeks ago. I'm currently planning to replace the air filter, front oxygen sensor, and fuel pressure regulator as potential next steps. If these don't resolve it, I may need to consider deeper issues like sensor calibration or fuel delivery.

Anonymous 2009-02-17 10:00

Don't overlook the brake booster hose for leaks—this can cause vacuum-related misfires and idle instability. Also check that the airbox intake isn’t obstructed. The 2002 GPX features a cold intake system routed externally; while it may look outdated, it's not inherently faulty.

Anonymous 2009-02-18 08:13

No vacuum leaks were found during inspection. I recently replaced the fuel pressure regulator and front O2 sensor. While removing the MAF sensor, I noticed the silicone seal was improperly seated—this has been reported in other forums as a known issue that resolves stalling after proper sealing. I'm returning the MAF sensor for reinstallation to verify if this fixes the problem. Another source suggests that if symptoms persist, injector cleaning or replacement may be needed, followed by checking the engine control module (ECM) settings. Is there any truth to these recommendations? Thanks again.

Anonymous 2009-02-18 12:35

P0101 indicates a mass or volume air flow circuit with range/performance issues. P0103 points to a high input in the mass/volume air flow sensor. To diagnose, use a multimeter to test the wiring harness connection from the sensor plug to the main connector—look for broken wires. Alternatively, use an OBD2 scanner to monitor real-time data while running the engine. Gently wiggle the wiring to see if readings fluctuate. I once found two broken wires in a 2001 3.4L Grand Am that caused similar symptoms.