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P0446 Diagnostic & Fix for 1997 Chevrolet Blazer 4.3L 4WD - EVAP System Issues

Model: 1997 chevrolet blazer Fault Code: P0446 Posted: 2015-03-11 13:29

I own a 1997 Chevrolet Blazer with 109,000 miles, equipped with a 4.3L V6 engine and 4WD. The vehicle consistently triggers the 'Service Engine Soon' light, which I've been able to temporarily disable by disconnecting the battery—though it returns within about one month. A diagnostic scan at AutoZone revealed fault code P0446: Evaporative Emission (EVAP) Vent System Performance Issue. The truck is primarily used for short trips, resulting in extremely poor fuel economy (around 10 mpg), and I've noticed engine misfires during operation. I've already had the fuel system cleaned at Jiffy Lube, which improves performance temporarily—though the effect lasts only a few months. I’ve replaced spark plugs, ignition wires, and oxygen sensors with no lasting resolution. I'm seeking reliable advice on the most common causes of P0446 in this model year and engine configuration to help resolve the issue permanently.

Related fault codes
P0446
Comments (3)
Anonymous 2015-03-11 16:09

P0446 refers to an Evaporative Emission (EVAP) System performance fault. The most common causes include: - A loose, missing, defective, or improperly fitted fuel tank cap - Incorrectly routed or damaged EVAP vacuum and vapor lines - A stuck-closed EVAP vent valve - A restricted or blocked EVAP hose - A malfunctioning or clogged fuel tank rollover valve For the 1997 Chevrolet Blazer with a 4.3L engine, these components are frequently found to be the root cause. Checking and replacing the fuel cap and inspecting vacuum lines are recommended first steps. Source: https://www.obd-codes.com/p044-6

Anonymous 2015-03-12 10:58

Thanks for the detailed explanation, Kev2! This has significantly improved my understanding of what to expect during a mechanic visit. I don’t have a lift, so I’ll focus on simple, doable checks first—like inspecting the fuel cap and vacuum lines. I’ve already verified that the fuel level is correct, replaced the gas cap, and confirmed no leaks or improper usage. This forum and resource are very helpful for DIYers like me. Appreciate it!

Anonymous 2015-03-12 10:59

Apologies—my earlier comment was incomplete; I meant to mention that fuses related to the EVAP system (such as the vacuum control module) should also be checked, especially if the issue persists after basic inspections. A blown fuse could cause intermittent P0446 errors in older 1997 Blazer models.