1996 Ford Mustang

Dear Doctor: I have a 1996 Ford Mustang 4.6-liter V-8 with the “check engine” light. Diagnostic test fault codes read evaporation system, shorted purge flow sensor, plus codes 171 and 174 (right and left cylinder banks running lean). I replaced the defective parts and cleared the fault codes. The car ran great for 60 miles, but the “check engine” light came back on. The same fault codes showed. The Mustang also has an aftermarket cold air intake system. Any advice? Bill

Dear Bill: The fault codes 171 and 174 are indeed lean codes. You need to find out when the codes were set what the readings were on the engine temperature and the engine speed. The use of a high-performance air filter can add to a lean condition, especially on late model vehicles. Intake vacuum leaks, or any vacuum leak, dirty mass air flow meters are all common culprits on Ford vehicles.

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