Where did my gas mileage go?

Asked by Jul 13, 2015 at 04:59 PM about the 1997 Kia Sephia RS

Question type: Maintenance & Repair

(previous post: Okay, so I'm completely car-ignorant. Just bought my first car.  Went
to take my
driving test in it, and my horn didn't work, so on the way to the shop to get it fixed, it
died. Had the alternator replaced. Turns out the horn didn't work b/c the ground was
corroded due to an oil leak. Replaced the valve gasket cover. Horn stopped working
again. Replaced it with a new one and it works fine. Out of nowhere, a day or two later
It started to die when it idled... when I pulled to the bottom of my driveway, or at stop
lights etc, but was fine when I would drive, and it would immediately start back up no
issue. It became more frequent, and then I couldn't even back out of my parking space
because it died the second I tried. Check engine light was NOT on. It didn't pull any
codes.  Disconnected the TPS, and it will run without dying at idle, but it's running
horrible (the OD off light is blinking at me, and the check engine light is on).

UPDATE: I reconnected the TPS, and my car hasn't died at idle.. yet. BUT it's running
pretty rough, it smells like gas when I start it, and when I park it, and my mileage has
CONSIDERABLY dropped (before all this, about 275-300 miles to a tank, and now
about 134).

What would be the first thing to check/the most likely suspect?

2 Answers

18,230

Try cleaning or replace ( IAC ) Idle Air Control Valve or Mass Air Flow Sensor. Also check the ( ETCS ) Electronic Throttle Control System- fuse. If this fuse is blown it will cause the vehicle to run badly like you said the vehicle is running. Also just recently ran into this problem and that was what the problem was. This fuse may be located in the fuse box under the hood.

44,665

Scan it for codes. Could be a bad O2 sensor or a leaky fuel injector or something else.

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