Extremely bad MPG

LISTER1989

MEMBER
2002 CHEVROLET MALIBU
V6
2WD
AUTOMATIC
195,500 MILES

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!

4 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

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

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Saturday, December 22nd, 2018 AT 12:33 PM

LISTER1989

MEMBER
8 POSTS

Hope I go about that? The engine sounds fine. Very smooth idle and drive.

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Sunday, December 23rd, 2018 AT 3:27 AM

LISTER1989

MEMBER
8 POSTS

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?

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Sunday, December 23rd, 2018 AT 4:37 AM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

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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