2007 Mazda 3 2.3L - terrible mileage

[northvanmazda3]

Been trying to figure out what to do about the mileage in my 2007 Mazda 3 2.3L hatchback. It has ~180000KM on it and has been a bit of a dog running at about 400KM per Fill up if I am lucky. on a bad fill up cycle i may get 320 KM or worse.... This has been a problem for about 18-24 months now with varying results. likely around 60/40 City/Highway ratio. Not a super aggressive driver but live at the top of the cut in North Vancouver, BC and do have to go down that hill a few times a week.

The only mod that I am aware of is K&N Cold air intake (was installed when i got the car used in 2012). Here is what I have done so far:

-MAF sensor wiring: i noted that the MAF wires were getting burned out at the connector and essentially broke on one of the 5 cables. I replaced the connector but did only a crimp job on the existing cable to the new cable/connector. probably about 2 years ago now. used to get tons of engine lights before this change.
-Purge Control Valve : replaced 2 years back.
-Washed out the K&N CAI filter and re-oiled as it was not replaced/cleaned for a long time (don't ask). Probably about 5 months ago when i did it.
-Spark plugs changed out 4 weeks ago.
-Replaced the K&N CAI drycharger bag as it has a large hole in it. 3 weeks new.
-converted the CAI to a short ram due to poor winter weather and to minimize the change of rain.
-MAF sensor replaced 3 weeks back as well.
-ran through a bottle of redline just in case.
-used to have some 225/50/18 rims but swapped to stock 16" winter rims with brand new Michelin cross climate 2's. (2 months old)
-engine light has come on /off periodically at different times but since the wash of the air filter, it seems to have gone away for the most part. When i do get one , it seems to go away after a few days on its own. I did not reset using the on/off method.

I have ordered a brand new CAI Filter as well as i am not sure if the original has buggered out, or cleaned it improperly/oiled it improperly. also ordered a new gas cap as another step.

What do you think? what else can i do here? not sure what else i can try here....

[G ~ MINI]

Injectors can be foul and not spraying correctly.
Do an fuel injector cleaner (I like the liqui moly fuel system cleaner)
Is your 2.3L burning oil ? Have you been checking the oil level regularly?

[TheMAN]

K&N filter could be the culprit... the 1st gen 3s don't play well with aftermarket intakes.... they could get bad readings due to air turbulence and cause the engine to run bad/rich

in any case, the 1st gen 2.3s are known to get bad gas mileage... the 2.5 in the 2nd gen were pretty bad too

[G ~ MINI]

K&N filter could be the culprit... the 1st gen 3s don't play well with aftermarket intakes.... they could get bad readings due to air turbulence and cause the engine to run bad/rich

in any case, the 1st gen 2.3s are known to get bad gas mileage... the 2.5 in the 2nd gen were pretty bad too

Good to know...learned something new today

[Flagrum_3]

Been trying to figure out what to do about the mileage in my 2007 Mazda 3 2.3L hatchback. It has ~180000KM on it and has been a bit of a dog running at about 400KM per Fill up if I am lucky. on a bad fill up cycle i may get 320 KM or worse.... This has been a problem for about 18-24 months now with varying results. likely around 60/40 City/Highway ratio. Not a super aggressive driver but live at the top of the cut in North Vancouver, BC and do have to go down that hill a few times a week.

The only mod that I am aware of is K&N Cold air intake (was installed when i got the car used in 2012). Here is what I have done so far:

-MAF sensor wiring: i noted that the MAF wires were getting burned out at the connector and essentially broke on one of the 5 cables. I replaced the connector but did only a crimp job on the existing cable to the new cable/connector. probably about 2 years ago now. used to get tons of engine lights before this change.
-Purge Control Valve : replaced 2 years back.
-Washed out the K&N CAI filter and re-oiled as it was not replaced/cleaned for a long time (don't ask). Probably about 5 months ago when i did it.
-Spark plugs changed out 4 weeks ago.
-Replaced the K&N CAI drycharger bag as it has a large hole in it. 3 weeks new.
-converted the CAI to a short ram due to poor winter weather and to minimize the change of rain.
-MAF sensor replaced 3 weeks back as well.
-ran through a bottle of redline just in case.
-used to have some 225/50/18 rims but swapped to stock 16" winter rims with brand new Michelin cross climate 2's. (2 months old)
-engine light has come on /off periodically at different times but since the wash of the air filter, it seems to have gone away for the most part. When i do get one , it seems to go away after a few days on its own. I did not reset using the on/off method.

I have ordered a brand new CAI Filter as well as i am not sure if the original has buggered out, or cleaned it improperly/oiled it improperly. also ordered a new gas cap as another step.

What do you think? what else can i do here? not sure what else i can try here....

Just stating your mileage per fill up tells us nothing. How many litres do you fill for those numbers. Calculate litres per 100km, and how many litres are still left. We have 55 litre tanks if I remember correctly.

What were those engine lights for, did you not scan it?

Have you tried resetting the computer after all those remedies, as in disconnecting the battery for ten minutes? Then driving casually for 1/2 hour.


_3

[Johns 08 3 GT]

K&N filter could be the culprit... the 1st gen 3s don't play well with aftermarket intakes.... they could get bad readings due to air turbulence and cause the engine to run bad/rich

in any case, the 1st gen 2.3s are known to get bad gas mileage... the 2.5 in the 2nd gen were pretty bad too

Yup. Left mine stock for that reason.

But the 2.3 was never a good engine for MPG's. Its funny that I could (almost) get my 400hp Hemi down to similar MPG's of that 2.3L. I got under 600 a tank mixed driving. My 18 2.5 gets the same range ish.

[northvanmazda3]

Thanks TheMan. I did not know that either. I am out of luck to return to the original intake as I purchased the car with only the CAI installed. I did not think that i would be getting this poor mileage though. most recent fillup to 5/8 full give me only 110K.... not good

[northvanmazda3]

i'll try and see if I can do the calc carefully in terms of the fillup in terms of litres. that and will have to run it to dry to get it close to a measurable number since i am not sure i can trust the levels in the gauge, unless i can go with that e.g. filled up 50 L, get to halfway after 150KM etc...

I was getting a bunch of engine running lean type of codes PO102, P0103, P0113. seemingly related to the MAF cabling. I do not see them any more now though....

i'll reset the computer again and see if it makes a difference and try to keep the driving easy for 30 minutes.

[G ~ MINI]

i'll try and see if I can do the calc carefully in terms of the fillup in terms of litres. that and will have to run it to dry to get it close to a measurable number since i am not sure i can trust the levels in the gauge, unless i can go with that e.g. filled up 50 L, get to halfway after 150KM etc...

I was getting a bunch of engine running lean type of codes PO102, P0103, P0113. seemingly related to the MAF cabling. I do not see them any more now though....

i'll reset the computer again and see if it makes a difference and try to keep the driving easy for 30 minutes.

All those code seem to lean towards a dirty / bad MAF or IAT intake air sensor and not CAI.
Faulty mass air flow sensor
Intake air leaks
Dirty mass air flow sensor
Dirty mass air filter
Mass air flow sensor harness is open or shorted
Mass air flow sensor circuit poor electrical connection

ECU pulling all those codes will likely put you in a limp mode which results in bad / not optimal MPH.