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jeffrey590, ASE Master Technician
Category: Car
Satisfied Customers: 2847
Experience:  ASE Master Technician , Saab Master Technician w/ 35 years Dealer Experience in Advanced Level Diag.
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2001 Mazda protege: 2.0L..mileage..rough idle, no acceleration

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2001 Mazda Protege 2.0L engine...102,000 mileage. Having episodes of rough idle, no acceleration (usually after car's been sitting overnight), CE light now stays on constantly. This has been problem for last year but no one can diagnose, it didn't code out until this week. Coding is P0300 (random misfire). Mechanic changed plugs and one coil. Runs better but still having acceleration problems intermittently. Seems to run a little better on higher octane fuel.
Submitted: 8 years ago.
Category: Car
Expert:  jeffrey590 replied 8 years ago.
I would recommend checking the fuel pressure on the vehicle and possibly replacing the fuel filter (if you havent already)...P0300 is a code for a random misfire(computer doesnt know which cylinder(s)are misfiring)...this can be caused by a lean fuel condition or an intake vacuum leak...usually when ignition breakdown is the cause,there will also be a cylinder specific misfire code stored as well(P0301,P0302,P0303 or P0304)...since your vehicle doesnt have this code I would tend to think its a lean misfire condition and troubleshoot accordingly...Fuel pressure , clogged fuel filter or vacuum leaks is where you want to go next....If you have access to a scn tool, you can monitor your fuel trim and get an idea what the computer sees and is adjusting for...jeffrey590
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