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Q: No power when accelerating

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I own a 5 speed manual fuel injected Kia Sephia. I bought it used and the check engine light was on. It ran perfectly,so I ignored the warning light. In a few months I felt a very small hiccup off and on when I accelerated. It wasn’t bad, so I let it go. After a month went by it started hesitating very noticeably when I was cruising with the gas pedal held at a steady speed. Then the hesitating got more and more frequent until it turned into bouts of heavy running of loud and slow - then it would run normally again. This happened off and on. I revved up the car to high speeds to keep it running at a normal pace because going slower caused it to hesitate. A few weeks later it did nothing but run loud, heavy and shaky when idling. It almost shut down when I pushed on the gas pedal. Revving it up to high speeds didn’t help it run normally anymore. Up until now when I start the car it runs heavy, shaky, loud and high revving does not good at all. I did replace the exhaust system, spark plugs, fuel filter, fuel pump, fuel pressure regulator, air pressure valve, air idle control. But none of these parts helped. I can no longer drive the Sephia because it has no power when accelerating, and the engine shakes and runs loud. I haven’t replaced the injectors, the injector wire harness, or the coils. Except I did replace the coils and the car still hesitated, so I took them back to the store. When my alternator belt broke I drove the car home. When I put a new alternator belt on all the problems returned. Can you please help me fix my car? Do you have any ideas what this could be? Thank you.

Hello! I believe the problem is likely to do with the mass air flow sensor. When this sensor is at fault it will be sending a regular error inlet reading which will cause computer to incorrectly apply air fuel ratio.

I recommend that you have the Check Engine Light checked by a qualified mechanic because that will potentially be a huge insight as to why the vehicle is being troublesome.

If the alternator belt keeps breaking you likely have an issue with one of your pulleys. Have a technician check your pulleys to ensure that they spend freely with little to no resistance. If any pulley displays resistance and does not move freely when it turns, then the pulley should be replaced as necessary. Good luck!

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