2003 Mazda Protege engine surges

2003 MAZDA PROTEGE
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ALIG0802
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2003 Mazda Protege 4 cyl Automatic 118000 miles

My car recently started increasing RPMs while i am maintaining a constant speed. It seems to do this around 45 mph and higher. It increases from 2.5/3 rpm to 3.5/4 and then goes back. I just replaced the air intake (air duct?) hose and also the o2 sensor. I have also had the transmission replaced about a year ago. The check engine light is not on. Any ideas of what it could be?
Apr 7, 2010 at 10:43 PM
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RASMATAZ
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Inspect and test all the following listed below and get back with some testing results we start here

Oxygen sensors.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard.
Apr 8, 2010 at 3:57 AM