Service engine soon light is on, when i give it gas or go up a hill the light flashes and it runs ruff and looses power
Because it's setting the code under those circumstances. Take it up to an auto parts store, they can read the codes for you. (or you can pay to have a mechanic or dealership do it). You can also buy an OBDII scan tool, the better ones will let you monitor codes as they happen while you're driving.
A flashing service engine soon light is warning you that the engine is misfiring and damaging the catalytic converter. Since it's misfiring under load that points to either you need a tune up, or an ignition coil pack is failing. If it turns out to be a failing coil pack, replace all 3. If one is bad, the other two are soon to follow. HTH. - Jim
Also this happened when a crankshaft/camshaft sensor started to fail. Try to find out the code.
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