Gas mileage fell off a cliff!

Rocket · 09-23-2009, 03:41 PM

The last four tanks have been terrible for gas mileage! I used to get 23 - 25 mpg, now I am getting around 20 mpg!

The only change I made was a new air filter. I'd expect mileage to improve. But it hasn't. Tire pressures are correct.

Any ideas? I'm thinking I'll check the air filter, but that seems unlikely.

Thanks!

**mazdaspeedster3** · 09-23-2009, 04:00 PM

Go to the auto parts store and get MAF Cleaner... Sometimes changing the air filter will throw your MAF off. It is easy to clean. Pull it, unplug it completely and then spray every bit of it with the cleaner, directions will tell you 15-20 good blasts. Then reverse install. That should help you out!

Robotaz · 09-23-2009, 04:31 PM

Quote:

Originally Posted by mazdaspeedster3

Go to the auto parts store and get MAF Cleaner... Sometimes changing the air filter will throw your MAF off. It is easy to clean. Pull it, unplug it completely and then spray every bit of it with the cleaner, directions will tell you 15-20 good blasts. Then reverse install. That should help you out!

That, and try just resetting the ECU by disconnecting the battery (-) terminal overnight.

Rocket · 09-23-2009, 04:54 PM

Where is the mass airflow sensor? I'll clean it and reset the ECU.

Robotaz · 09-23-2009, 07:46 PM

Quote:

Originally Posted by Rocket

Where is the mass airflow sensor? I'll clean it and reset the ECU.

It's on your air intake. Look between the air filter and the throttle body for a part with a plug that goes to the computer. Carefully take the plug off, and I'm assuming it will have a couple of screws that you remove and the MAF will come right out. Go buy MAF cleaner. It's a spray can of liquid that is safe for electronics.

Rocket · 09-23-2009, 08:05 PM

I went out and cleaned it. Though it is dark now, it was visibly dirty. Battery is disconnected, I'll hook it back up tomorrow. Thanks amigos!

Robotaz · 09-23-2009, 08:23 PM

Quote:

Originally Posted by Rocket

I went out and cleaned it. Though it is dark now, it was visibly dirty. Battery is disconnected, I'll hook it back up tomorrow. Thanks amigos!

Let us know what happens.

**coolmazda5** · 09-23-2009, 11:30 PM

Maybe coincidence, but Have you tried a different gas station just in case? I've experienced that before...

Rocket · 09-24-2009, 05:52 AM

Yes, I've shopped around. I rarely use the same station. That was my first thought also, but four tanks later it is just getting worse.

I'll know today or later this week if there has been an improvement.

Rocket · 09-24-2009, 08:50 AM

Too early to tell if the mileage has improved, but the car stalls when coming to a stop. It has happened about 10 times so far this morning.

Robotaz · 09-24-2009, 10:55 AM

Quote:

Originally Posted by Rocket

Too early to tell if the mileage has improved, but the car stalls when coming to a stop. It has happened about 10 times so far this morning.

You did use MAF cleaner, right? Did you blow the MAF out with air and do everything you could to dry it? I would check it again tonight to see if it's dry. I noticed last time that I used MAF cleaner that it didn't evaporate quickly like throttle body or brake cleaner. Maybe it's still wet or something.

Rocket · 09-24-2009, 04:16 PM

I used MAF cleaner. It sat overnight, I'm sure it was dry.

Anyway, no stalls this afternoon. I filled the tank, I'll know in a day or so if the mileage has improved since I drive about 100 miles per day (car has 93,000 miles!).

Thanks for the tips!

diogenes · 09-24-2009, 08:02 PM

I sometimes get poor mileage this time of year when the stations switch to "winter gas" with more alcohol in the mix, which is required to address air quality issues. Alcohol has less energy per volume than gasoline, so mileage suffers. That's good advice above about cleaning the MAF sensor, though, especially since you've already addressed the most likely problem by changing the air filter

Rocket · 09-30-2009, 04:48 PM

As a follow up, the mileage is still not where I'd like it to be. Today was 21.2, compared to an average in the 23.5 range. I'm going to take another look at the air filter and replace it with another brand. While it is hard to imagine that a new filter would cause the problem, I am going to undo the last thing I did and see what happens.

Stay tuned...

harrye357 · 09-30-2009, 06:08 PM

Quote:

Originally Posted by Rocket

The last four tanks have been terrible for gas mileage! I used to get 23 - 25 mpg, now I am getting around 20 mpg!

The only change I made was a new air filter. I'd expect mileage to improve. But it hasn't. Tire pressures are correct.

Any ideas? I'm thinking I'll check the air filter, but that seems unlikely.

Thanks!

Hello,
Had a similar problem on my 95 Protege. Turns out that the ebrake cable was stuck and the right rear brake was dragging.
Harry

09-23-2009, 03:41 PM	#1
Rocket Registered User Join Date: Apr 2006 Posts: 269	Gas mileage fell off a cliff! The last four tanks have been terrible for gas mileage! I used to get 23 - 25 mpg, now I am getting around 20 mpg! The only change I made was a new air filter. I'd expect mileage to improve. But it hasn't. Tire pressures are correct. Any ideas? I'm thinking I'll check the air filter, but that seems unlikely. Thanks!

09-23-2009, 04:00 PM	#2
mazdaspeedster3 The All Knowing... MazdaV.com Moderator Mazdaspeed3. 2008 Join Date: Apr 2008 Location: Walled Lake, MI Posts: 6,724	Go to the auto parts store and get MAF Cleaner... Sometimes changing the air filter will throw your MAF off. It is easy to clean. Pull it, unplug it completely and then spray every bit of it with the cleaner, directions will tell you 15-20 good blasts. Then reverse install. That should help you out! __________________ For Sale... http://www.mazdas247.com/forum/showt...hp?t=123775515

09-23-2009, 11:30 PM	#8
coolmazda5 Look Mom, A Real Clutch! Donated: $15 Mazda5 & Hybrid Mazdas Moderator 2006 and 2008 Mazda5s 5MT Sport w/ Popular Package Join Date: Oct 2006 Location: Wawa Land (NE US) Posts: 4,839	Maybe coincidence, but Have you tried a different gas station just in case? I've experienced that before... __________________ - 2006 Mazda5, 5MT Sport, Carbon Gray, Popular Package, OEM Fogs. OEM Cargo Cover - 2008 Mazda5, 5MT Sport, Stormy Blue Mica, Popular Package, Aux Input, TPMS, The Thule Roof Rack Works, *MAZDASPEED* Shift Knob [How to Search & Post]

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09-23-2009, 04:54 PM	#4
Rocket Registered User Join Date: Apr 2006 Posts: 269	Where is the mass airflow sensor? I'll clean it and reset the ECU.

09-23-2009, 08:05 PM	#6
Rocket Registered User Join Date: Apr 2006 Posts: 269	I went out and cleaned it. Though it is dark now, it was visibly dirty. Battery is disconnected, I'll hook it back up tomorrow. Thanks amigos!

09-24-2009, 05:52 AM	#9
Rocket Registered User Join Date: Apr 2006 Posts: 269	Yes, I've shopped around. I rarely use the same station. That was my first thought also, but four tanks later it is just getting worse. I'll know today or later this week if there has been an improvement.

09-24-2009, 08:50 AM	#10
Rocket Registered User Join Date: Apr 2006 Posts: 269	Too early to tell if the mileage has improved, but the car stalls when coming to a stop. It has happened about 10 times so far this morning.

09-24-2009, 04:16 PM	#12
Rocket Registered User Join Date: Apr 2006 Posts: 269	I used MAF cleaner. It sat overnight, I'm sure it was dry. Anyway, no stalls this afternoon. I filled the tank, I'll know in a day or so if the mileage has improved since I drive about 100 miles per day (car has 93,000 miles!). Thanks for the tips!

09-24-2009, 08:02 PM	#13
diogenes Registered User Join Date: Dec 2006 Posts: 27	I sometimes get poor mileage this time of year when the stations switch to "winter gas" with more alcohol in the mix, which is required to address air quality issues. Alcohol has less energy per volume than gasoline, so mileage suffers. That's good advice above about cleaning the MAF sensor, though, especially since you've already addressed the most likely problem by changing the air filter

09-30-2009, 04:48 PM	#14
Rocket Registered User Join Date: Apr 2006 Posts: 269	As a follow up, the mileage is still not where I'd like it to be. Today was 21.2, compared to an average in the 23.5 range. I'm going to take another look at the air filter and replace it with another brand. While it is hard to imagine that a new filter would cause the problem, I am going to undo the last thing I did and see what happens. Stay tuned...