Base model Impreza with ridiculous fuel consumption!

[Porsche Liebhaber]

Hello everyone!

I have a 2008 1.5 litre automatic Impreza that has an unusual fuel consumption.
Owner's manual says it should do 12 km/litre avg. and at worst 10 km/litre, what I'm getting is 7 km/litre at best. The car is used, it had 82,000 km when bought, now it has 128,000 and the issue is getting worse over time. And I can't afford going to the dealer these days BTW.

Things I've done ( that made no difference) :
-Engine oil & oil filter changed (5w-30 synth)
-Engine air intake filter changed
-MAF sensor cleaned
-Both O2 sensors checked (fine)

I'm thinking about buying a WiFi OBDII scanner, would it help?

 

[argatoga]

It does sound to me that a sensor is causing it to run rich. I'd wait for Spectre to jump into the thread, but the MAF may need to be replaced.

 

[Spectre]

Coolant temperature sensor or air temp sensor are likely candidates - also, while your O2 sensors might be 'fine' at 128k km, they should be replaced as they're at the generally accepted service limit.

 

[Porsche Liebhaber]

Coolant temperature sensor or air temp sensor are likely candidates - also, while your O2 sensors might be 'fine' at 128k km, they should be replaced as they're at the generally accepted service limit.

Would the OBD2 scanner help to determine the culprit?
And can the spark plugs cause that if they're old? Because I didn't change them since I bought it at 82k km.

- - - Updated - - -

It does sound to me that a sensor is causing it to run rich. I'd wait for Spectre to jump into the thread, but the MAF may need to be replaced.

OK thanks

 

[Spectre]

Not necessarily - bad temp sensors rarely set codes. And it is possible for plugs to affect fuel economy, but only if you're already getting misfire or they're so bad you're not getting a strong spark. Check your manual to see what plug change intervals are supposed to be, though.

 

[Porsche Liebhaber]

No misfire, but there is a weird delay/hesitation at 1500 RPM when the AC is on and the car is hot, it happens when I accelerate hard it gets to 1500 RPM then it cuts the throttle for about 2 seconds. And also at 2500 RPM .

 

[Spectre]

Yeah, check your coolant temperature sensor. If you have two, one will be for the gauge on your dash and one will be for the EFI system; it's the second one you want to look at.