engine idles up and down

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2000 mazda b4000 pickup engine idles up and down like the air conditioner compressor is coming on then going off. truck runs good but bad gas mileage, 14 or 15 mpg, v-6. engine light won't go off. new mass air flow filter, 4 oxygen sensors, new gas cap, and fuel injector clean added. Still engine light is on. Code is P0174. What could cause lean air/fuel ratio? What does lean/rich/limit stop mean? Any suggestions will be appreciated.

jrbone in Rice TX

Feb 2, 2011

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RepairPal Certified shops can diagnose and repair your 2000 Mazda B4000. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.

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engine idles up and down

What is your question?

jrbone in Rice TX

Feb 2, 2011

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patrick mannionon Feb 2, 2011

Air flow meter has a huge impact on Air/Fuel ratio, front O2 sensors trim the air/fuel ratio, it would be important to look for vacuum leaks around the intake manifold or attaching vacuum hoses. A professional grade scan tool can read trouble codes, pending trouble codes and more important it reads live sensor data without having to do intrusive testing at each sensor. Chase vacuum leas next, insufficient fuel pressure volume/pressure could set a lean code but you would probably feel a loss of power.

jrboneon Feb 3, 2011

There is no loss of power at all. The motor runs great. Engine idling up and down continuously, bad gas mileage. I will have mechanic check for vacuum leaks around the intake manifold and check vacuum hoses. I hope there isn't a problem with the fuel ingectors.?? Thank you for your help. I will let you know what mechanic says and/or does.

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Popular Answer

What are the best Mazda repair shops?

RepairPal Certified shops can diagnose and repair your 2000 Mazda B4000. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.