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Discussion Starter #1
hi all

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.
-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.
-Spark plugs changed out 4 weeks ago.
-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 wel as i am not sure if the original has buggered out. 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....

tks
 

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engine light has come on /off periodically
What code(s)? I'd be interested to see the quality of the crimp connections at the MAF; I think that sensor (as are most all engine sensors) is sensitive to voltage/resistance, and that could be an insidious problem if the repair isn't rock-solid.
 

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With that distance on the odometer, change the Oxygen sensor. Be sure and use a proper tool made for it. The pre-catalyst is the one to target. If that is going bad, it won't trigger a code yet but what it tells the computer based on a wrong view will lead to more fuel being dumped in. If that doesn't fix the issue, you won't be out much money.
 

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As has already been suggested, lose the L&N CAI and go back to a factory intake (which was also a CAI), clean or replace the MAF, and replace the upstream O2 sensor with either an OEM or Denso sensor (do not use Bosch).
 

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Discussion Starter #7
What code(s)? I'd be interested to see the quality of the crimp connections at the MAF; I think that sensor (as are most all engine sensors) is sensitive to voltage/resistance, and that could be an insidious problem if the repair isn't rock-solid.
i did have another look at it today, and saw that the middle of the 5 wires at one end of the crimp was doing really poorly e.g. one or threads of the wire were remaining and the rest of it snapped off. I removed the crimp and re-did it. seems pretty solid and the rest of them appear to be good.

after driving again, i noted the following ECU codes. P0102, P0103, P0113.
not sure if those showed up before my change of the crimped section so will need to drive it a bit more, as i only put in a few KM today.

will see how this goes.
 

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Discussion Starter #8
With that distance on the odometer, change the Oxygen sensor. Be sure and use a proper tool made for it. The pre-catalyst is the one to target. If that is going bad, it won't trigger a code yet but what it tells the computer based on a wrong view will lead to more fuel being dumped in. If that doesn't fix the issue, you won't be out much money.
thanks for the advice here. I will do some investigation to see if it is something i can do, or have to get someone with a lift /risers to help out.
 

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As has already been suggested, lose the L&N CAI and go back to a factory intake (which was also a CAI), clean or replace the MAF, and replace the upstream O2 sensor with either an OEM or Denso sensor (do not use Bosch).
thanks for the advice. I would love to put the original back but as i purchased the car with the K&N CAI as is, i'm kinda stuck without going to the wreckers yard to get the needed parts again. Not impossible but still a bit of work. when we got the car, it was averaging 9.8-10.0 L /100km (according to the onboard gauge and aware of its limited accuracy) but now heading in the 13.0L end right now..... so guessing it is actually a bit worse.

i'll try the O2 sensor if I have the ability to do so.
 

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after driving again, i noted the following ECU codes. P0102, P0103, P0113.
As you may know, P0102 and P0103 are consistent with MAF connector fault(s); P0113 is for the IAT (intake air temperature, sensor circuit high input), and it is also consistent with a poor MAF connection.

If you feel confident in the connections now, I'd clear those codes. See if they return, and see if your fuel consumption returns to normal.
 

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I had a very difficult time troubleshooting a similar problem a few years ago. Was getting an intermittent P2188 code. I replaced many of the things you've already replaced with no change. I eventually ran across TSB:01-006/06 that mentioned a poor connection between the terminal and harness wire for the MAF. There is a kit for replacing one the pins on the connector. It ended up fixing it for me.

I think you're on the right track to clean up your MAF wiring. Afterwards, if you still get nagging codes, in particular, P0172, P2178, or P2188 do a google search for TSB:01-006/06 and you'll find everything you need for that repair.
 

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Discussion Starter #12
hi all. after some more work and other weird maintenance, i seem to be back where i started. I will now have to look at just getting the wiring completely redone. I am not sure where the wiring goes on teh car end but getting sick and tired about having this lingering. this sounds like something that I will need to go to a shop to do since I want to put the onus on someone else to 'own' the issue.

TO recap:

-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 + wires as the new connector came with 6 inches of wiring. so essentially crimped the car end of the wiring to the 6 Inches of new ones + connector.
-Changed the MAF sensor itself 2 months back
-Purge Control Valve : replaced 2 years back.
-Have a K&N CAI + Drycharger. I do not have the original air filter assembly as it came this way when i bought the car used. Replaced both the K&N Filter + Drycharger bag in the past few months.
-converted the CAI to a short ram due to poor winter weather and to minimize the chance of water getting into the system.
-Spark plugs changed out 2 months ago.
-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. (3 months old)
-Engine light has not come on and there are no longer any codes.....
-Changed the gas cap with OEM one.

This car is driving me NUTS! with the most recent fill up i have only gotten 110KM with 3/8 tank of gas used.... ridiculous!
 
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