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P0172 Fault on 1995 Blazer: Diagnosis and Solutions for Rich Fuel Condition

Model: 95 Blazer Fault Code: P0172 Posted: 2006-06-29 09:48

I frequently encounter the P0172 diagnostic trouble code on my 1995 Chevrolet Blazer. The Check Engine Light appears intermittently, turning off after 3 to 5 restarts, then reappearing after several days of no symptoms. This vehicle does not have a Mass Air Flow (MAF) sensor, so that is ruled out. I've already performed a thorough inspection: cleaned the throttle body, checked for vacuum leaks, and verified fuel pressure—all results are within normal ranges. The engine runs smoothly with no noticeable driveability issues, though there may be slight differences in performance when the code appears. Given the absence of a MAF sensor, I suspect the issue lies elsewhere. I previously replaced the spider fuel injector due to visible burnt fuel residue at the intake manifold bottom—this component is known for being unreliable and poorly designed. Despite this replacement five years ago, the problem persists. I've also replaced both oxygen sensors (pre- and post-catalytic converter), swapped them around to test responsiveness, and confirmed no change in behavior. I’ve replaced the ignition module, coils, plug wires, and spark plugs—none of these fixes have resolved the issue. Fuel pressure remains stable at approximately 43 psi when running, with no signs of leakage or drop-off. I recently installed a K&N air filter and intake system to improve airflow, but this did not resolve the problem and only increased maintenance costs. Next step: I plan to inspect all ground connections for corrosion or poor contact. If that doesn- t help, I may take it to a professional shop for further diagnostics. Any additional insights or suggestions would be greatly appreciated.

Related fault codes
P0172
Comments (2)
Anonymous 2006-06-29 13:33

The fuel spider is indeed a common culprit in older Blazer models—especially with Vortec engines. However, double-check if your vehicle actually has a MAF sensor; some early Vortecs did include one despite being marketed as MAF-less. Also consider the possibility of issues with the oxygen sensor, exhaust gas temperature (EGT) sensor, coolant temperature sensor, or throttle position sensor (TPS). Fuel pressure regulator failure is another potential cause. Could you confirm your fuel pressure reading? Is there any sign of fuel bleeding off under load?

Anonymous 2006-06-30 07:03

Confirmed—no MAF sensor on this model; MAP sensor present, but not MAF. I've tested both O2 sensors and swapped them to see if the P0172 code followed one specifically—it did not. All ignition components (module, coils, wires, plugs) have been replaced with no improvement. Fuel pressure is stable at 43 psi when running, and there's no noticeable drop or leakage. The spider injector was replaced five years ago due to visible burnt fuel in the intake—this has been a recurring issue for me. I installed a K&N air filter and intake system hoping to improve airflow, but it made no difference and only added cost. I'm now going to inspect all ground connections thoroughly. If that doesn't resolve it, I'll consider taking it to a professional shop for deeper diagnostics. Any other ideas or testing steps would be very helpful!