Extremely bad MPG

2002 CHEVROLET MALIBU
195,500 MILES • V6 • 2WD • AUTOMATIC
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LISTER1989
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I've been trying to fix this problem for over a year. I've changed the plugs, used expensive fuel system cleaner, kept the oil good, made sure there's no brake drag, checked for leaks, over filled the tires slightly, changed air filter, and any other tricks I could find. But all to no avail. I am getting 8 MPG.

I'm at a loss here.

P.S. I also ran a code scanner and the only thing that came up was a sticky thermostat. But that wouldn't reduce my MPG by more than half.

Please help!
Dec 22, 2018 at 3:19 AM
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JACOBANDNICKOLAS
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Hi and thanks for using 2CarPros.

Wow! That is bad! Have you checked to make sure there are no leaks? Is the air filter box good and nothing partially blocking the air induction tube? Is the car running good other than the bad mileage?

If you have a live data scanner, can you tell me the fuel trims (STFT and LTFT)? I mention this because you said you scanned the computer for codes and these readings will tell me if the computer is trying to compensate for a problem.

If the temperature sensor is telling the computer inaccurate coolant temp readings, it can cause the computer to compensate and run the engine with a really rich fuel mixture. So, the sticking thermostat could have a hand in it, but I agree with you. It shouldn't be that bad.

Also, have you confirmed the catalytic converters aren't plugging?

Let me know.
Joe
Dec 22, 2018 at 12:33 PM
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LISTER1989
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Hope I go about that? The engine sounds fine. Very smooth idle and drive.
Dec 23, 2018 at 3:27 AM
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LISTER1989
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I ran the code again and it came up with P0113, which says it's a IAT sensor. Would that cause it to be so low?
Dec 23, 2018 at 4:37 AM
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JACOBANDNICKOLAS
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I have to be honest, I don't think any one thing can cause it to be that bad. However, it wouldn't hurt to replace the sensor if it is indicating an issue.

Here are the directions for replacement:

PROCEDURES
INTAKE AIR TEMPERATURE (IAT) SENSOR REPLACEMENT

REMOVAL PROCEDURE

1. Disconnect the IAT sensor electrical connector.
2. Carefully grasp the sensor and with a twisting and pulling motion, remove the IAT sensor from air intake duct.

INSTALLATION PROCEDURE


1. Install the IAT sensor, snap the sensor into place.
2. Connect the IAT sensor electrical connector.

Let me know if this helps.

Joe
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Dec 23, 2018 at 6:02 PM