Horrible Gas Mileage

TheStuartKid

Member
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2008 mazdaspeed3
So now all the sudden im only getting 120 miles per tank... Yeah i get on it once in a while but i used to do the same and i would be getting 230 miles per tank.. What the hell happened? Need help please. Looking to be changing my spark plugs soon and going one step colder.. hopefully that will help with gas mileage and even smoking turbo once in awhile.
 
Ouch! Im complaining at getting on 220-240 avg to a tank. Clean filter, check tire pressure, clean maf, check O2 sensor??
 
Seriously? I'm getting about 180 on a half tank... Thats with stock OEM plugs with 91k on them
 
Need more info. Any other change in performance? Any unusual sounds? Is exhaust making smoke, and if so what color? All the time smoking or just when idling or just when WOT? Change in fuel or gas station? Dirty intake filter? Any CEL? Do you smell raw fuel anywhere? Is it dumping fuel into oil? Does oil smell like gas or is dipstick overful? When you pull plugs are any of them wet or other evidence of running excessively rich? Just a few of many, many possibilities on limited info provided.
 
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So now all the sudden im only getting 120 miles per tank... Yeah i get on it once in a while but i used to do the same and i would be getting 230 miles per tank.. What the hell happened? Need help please. Looking to be changing my spark plugs soon and going one step colder.. hopefully that will help with gas mileage and even smoking turbo once in awhile.

I am getting about 280-320 on my Cobb Economy tune driving about 80 to work with the MSCAIv2. (Shifting before 3k, less than 25% Throttle)

http://www.accessecu.com/accessport/mazda/AP-MAZ-002/MS3-MS6-MPS Service Bulletin.pdf

Have a look at that, Mazdaspeeds have a serious Carbon buildup problem. Mazda charges about 99 bucks to clean the valves, but with that guide you can do it yourself. ...But if you don't feel comfortable, don't do it.

Here are some things to slow the carbon problem down:
Aftermarket Turbo Inlet Hose
Adding 100RPM to your tune at idle (Helps the crankcase vent at idle)
Running Nitrogen Enriched Gasoline (Shell 93 or BP 93 work best)
Having the valves cleaned.
Changing your oil at frequent intervals
Using good oil (avoiding sludge)
Changing Plugs every 50k, cleaning every 25k. (NGKs IX regapped to .028 are a good alternative to iTV22s)

After everything above, I still have some build up. Just something you can look into. Have a look at that guide.

Other measures (Use at your own risk):
A small amount of Methanol Injection
Seafoam (Not recommened)
 
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Need more info. Any other change in performance? Any unusual sounds? Is exhaust making smoke, and if so what color? All the time smoking or just when idling or just when WOT? Change in fuel or gas station? Dirty intake filter? Any CEL? Do you smell raw fuel anywhere? Is it dumping fuel into oil? Does oil smell like gas or is dipstick overful? When you pull plugs are any of them wet or other evidence of running excessively rich? Just a few of many, many possibilities on limited info provided.

the colder plugs will chill the wetness right off

I go two steps colder in the winter
 
Exhaust is making smoke, once i changed from a hypertech to an accessport it started smoking consistently. We took out my o2 sensor and cleaned that and it stopped the jerking that i was getting and helped the gas mileage a little, nothing much though. @badinfluence how do i increase the idle +100 on top of what the accessport already does. Im idleing around 900 right now.
 
So you are running AP and the issues arose after dumping HT. Probably do not have your tune dialed in or have the wrong OTS map selected or have not done MAF calibration.

Maybe flash back to stock and see if problem goes away, then get professional AP tuner help. Or go back to HT and get 99% of the performance level on stock turbo and pump gas hassle free.
 
Exhaust is making smoke, once i changed from a hypertech to an accessport it started smoking consistently. We took out my o2 sensor and cleaned that and it stopped the jerking that i was getting and helped the gas mileage a little, nothing much though. @badinfluence how do i increase the idle +100 on top of what the accessport already does. Im idleing around 900 right now.

The Cobb Accessport already does this for you.

Are you trying to run Stage2 without a CDFP?

My guess is either your clogged with carbon or something is wrong with the way your tune is working. (Calibration, Mods, ETC)

http://www.mazdas247.com/forum/showthread.php?123820566-Accessport-maps&p=6031306#post6031306
I noticed in the other thread you asked about stage 2 with the MSCAI. You MUST pick the right tune for the intake otherwise the MAF will not read right and piss your car off.

Stage 2 requires a FULLY FUNCTIONAL CDFP (make sure yours is holding if you already have a upgraded one)

Do a light pull, but don't hit it to hard, it sounds like your engine is really pissed. Full free to send me the datalog or post it and I am sure we can figure it out.

This is what I found for your mods, is it still accurate? (Obviously Minus the Hypertech)
turboxs catless downpipe/racepipe, mazdaspeed CAI, cobb TIP, PTP HPFP internals, and hypertech tune

The upgrade from MSCAI to MSCAIv2 is a 18 dollar piece of plastic and is very worth it to for the gas milage increase. I went up 4mpg when I added that piece of plastic.

I have the MSCAIv2 and if you try to run a MSCAIv1 map or Vice Versa it is BAD. Also if you have a MSCAIv2 and the straighter isn't straight it will also make the MAF not read right. I used some hi temp epoxy to keep mine in place.
 
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And there is a right and wrong way to index or "clock" that plastic air straightener. Mine had a dot on the outside of the plastic piece that you line up with a corresponding dot or mark on the tube. It matters if you want your MAF calibration right.

OP: maybe avoid multiple mod changes at the same time or close to each other? You come on the board, report yet another in a series of seemingly never ending problems, raise a short cryptic complaint, and then after a series of efforts by us to get more info we find out that you keep changing things. We go off on a wild goose chase only to find out that you have made other changes.

Now we know you switched to AP. Nothing wrong with that, but should have told us. Then we find out you have loaded the wrong map for the wrong intake and don't seem to understand where to get the MSCAI map or which one you need.

We knew you were at stage 2 with your mods but don't know if you have upgraded your fuel pump internals which is absolutely essential to run AP stage 2 maps.

Your wide band O2 sensor got fouled. You cleaned it without exploring why it fouled.

Are there any more surprises out there you intend to getting around to sharing?

Please consider flashing back to stock, which I believe is AP zero, or reinstalling your HT flash until you get the engine operation and fuel consumption issues resolved and a stable baseline in place. I respectfully ask you to NOT add any new mods, not even pump internals (if not already done), until the other issues are resolved.

Finally, please edit your signature to list your current mods so that when you ask for help we do not have to read or reread all your posts to figure out what you've done to your car. If you have multiple threads open with different issues in each one without telling us about the others we have to chase all over the place to try to make some sense of what is going on with your car.

Can you understand why I am frustrated and wonder why I should try to continue to help you?
 
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And there is a right and wrong way to index or "clock" that plastic air straightener. Mine had a dot on the outside of the plastic piece that you line up with a corresponding dot or mark on the tube. It matters if you want your MAF calibration right.

OP: maybe avoid multiple mod changes at the same time or close to each other? You come on the board, report yet another in a series of seemingly never ending problems, raise a short cryptic complaint, and then after a series of efforts by us to get more info we find out that you keep changing things. We go off on a wild goose chase only to find out that you have made other changes.

Now we know you switched to AP. Nothing wrong with that, but should have told us. Then we find out you have loaded the wrong map for the wrong intake and don't seem to understand where to get the MSCAI map or which one you need.

We knew you were at stage 2 with your mods but don't know if you have upgraded your fuel pump internals which is absolutely essential to run AP stage 2 maps.

Your wide band O2 sensor got fouled. You cleaned it without exploring why it fouled.

Are there any more surprises out there you intend to getting around to sharing?

Please consider flashing back to stock, which I believe is AP zero, or reinstalling your HT flash until you get the engine operation and fuel consumption issues resolved and a stable baseline in place. I respectfully ask you to NOT add any new mods, not even pump internals (if not already done), until the other issues are resolved.

Finally, please edit your signature to list your current mods so that when you ask for help we do not have to read or reread all your posts to figure out what you've done to your car. If you have multiple threads open with different issues in each one without telling us about the others we have to chase all over the place to try to make some sense of what is going on with your car.

Can you understand why I am frustrated and wonder why I should try to continue to help you?

Spot on.

OP: Another thing I see that I just noticed is that you went Catless! This can be a slipery slope for this car if it is not reading right. The car can hit fuel cut at 19 without a Cat without quickly. I have been told by Cobb that OTS do not support Catless exhausts! Even their kit comes with one. Similar problems with Fuel Cut, Tune issues, Flow problems, and bucking occur without a custom tune on catless setups. I would start there because that will prevent you from finding the real issue if it isn't the issue itself. (Can't go back to 0 with Catless)
 
^ Excellent advice. But, FWIW catless dp/rp does work well with HT's load based tuning, or at least it does for me with my mods - no cut of any kind with boost maxing out just short of 19 psi. But he needs to go back to stock tune one way or the other to sort out what is going on and work from there. Stock tune will not be producing his terrible gas mileage. Ultimately mileage is most greatly influenced by how aggressively and frequently you push the "go pedal" assuming that everything else is running right.

Hell, with my mods I get between 27 to 29 highway mpg running between 75 and 80 mph, and combined city/highway driving is usually 22-23. I usually get about 280-300 miles on a tank on combined city/highway driving and I'm damn near fully bolted and drive the s*** out of this car with multiple WOT's just about every day.

EDIT: IIRC, OP has had his downpipe on and off several times, each time requiring removal of the primary (wideband) O2 sensor. As you know that sensor provides info for a huge amount of the ECU's different functions. I'd not be surprised to eventually find out that it has been damaged, that this may be why it is fouling, and that it is not capable of sending accurate info to the ECU and is responsible for a huge array of different problems he is having. But that is just speculation at this point.
 
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