2002 Mazda Protege Lean Air/Fuel Ratio

SCHECTERGUY

MEMBER
2002 MAZDA PROTEGE
4 CYL
FWD
MANUAL
185,000 MILES

So my check engine light comes on. I take the car to Advance Auto Parts and have them run a diagnostic. Two codes say lean air/fuel ratio, one code says random cylinder misfire detected, another sais heated O2 sensor - low input and another sais VTCS. The guy at advance tells me it is most likely a result of low fuel pressure. Another possible problem according to the print out was VTCS valve stuck open. As far as performace goes, i've noticed its much harder for the cluth to catch in first gear. Also I've noticed a slight decrease in fuel mileage. One thing I know is wrong is I have a busted front exhaust pipe. Any ideas as to what the problem is?

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)