Gas milage

[ruskeyjdm]

I been getting horrible gas milage, and with these high prices its killing me. I can literally watch my needle go down. I drive decent speeds almost everywhere i go? any clue as to what it could be linked to?
I drove it up from Florida and was getting decent milage, halfway into GA, my CEL came on and it seemed to start after that. any help would be appreciated

 

[sean22306]

Whats the CEL code? I'm sure figuring out the code will tell you the issue.

 

[tweakingmsp]

I too am getting terrible gas mileage. Before when I got down to half tank, I was around 200 miles on my trip. I just noticed today that I have half a tank, and I'm only at 120 miles. IMHO, I think the higher the gas prices go, the cheaper the gas is made. That way you have to fill up more, and they make more money.

A guy I know took some gas from the pump, and took it straight to a lab to have it tested. It turned out that there was a very large amount of algae in the gas. I'd say that would be one reason to getting crappy gas mileage.

 

[ruskeyjdm]

Well when i got home, i fixed a leak in the exhaust, (before the midpipe) and i reset the ECU, i havnt have the CEL come back on since, but the gas milage succkkkssss.

 

[MSP2226]

Alot of gas stations are mixing their gas with 10% ethanol. I think that is contributing to the bad gas mileage also.

 

[Spooler]

Some basic things to save some gas: Check your tire pressure, make sure your spark pugs are in good condition and gapped right, replace (or clean) your air filter regularly. But the fact that you have a CEL makes me think you have something else afecting your gas milage.

 

[ruskeyjdm]

yeah it was weird, i was getting great mileage, and then when the CEL came on, it seemed to just drop off, i pulled over to get gas like 2-3 times. (not always full tank)
could a vaccuum leak affect it at all?
temp differance? FLA to SC

 

[greasemonkey524]

An O2 sensor would cause those problems also.

 

[mazdaspeedwerx]

I say goto autozone and check the code. it probally is one of the o2

 

[ruskeyjdm]

The CEL came back on again today and i ran it up to Advance and they checked it....
PO421 Warm up Cat. Below Threshold. Bank One
so i take it that my downstream o2 sensor is shot?
too bad its like 250$ and my car seems to run even worse
any ideas?

 

[MSP #167]

The CEL came back on again today and i ran it up to Advance and they checked it....
PO421 Warm up Cat. Below Threshold. Bank One
so i take it that my downstream o2 sensor is shot?
too bad its like 250$ and my car seems to run even worse
any ideas?

do you have a cat, if so its shot.

 

[ruskeyjdm]

Well i got the catless midpipe. But other than that the exhaust is stock.
Is it the o2 sensor?

 

[MSP #167]

how long ago did you install the catless midpipe? the 02 sensor is throwing a code because it doesn't see a cat.

 

[ruskeyjdm]

Well it was on the car when i got it so i dont know exactly.
Is there a way to bypass it since i dont have any cats?
Could that code be a reason for the horrible gas milage i been getting?

 

[MSP #167]

Well it was on the car when i got it so i dont know exactly.
Is there a way to bypass it since i dont have any cats?
Could that code be a reason for the horrible gas milage i been getting?

yes,

1. what you can do is get a mil eliminator that you can wire into the 02 sensor

OR

2. What you do is go to the auto parts store pepboys/autozone or where ever and get 2 spark plug non foulers 18mm, ask for them if you can't find them.
Then what you do is drill one out all the way through so you can screw your 02 sensor into it you will need a pretty thick drill bit. once you do that screw them together and screw them into your 02 sensor bung on the exhaust and then screw the 02 sensor into them.

What this does is take the 02 sensor out of the exhaust so it is not reading as much raw fumes as if it was in the exhaust itself.

My friend with a GTI and myself have done this and we have not had our cat codes return.

 

[ruskeyjdm]

yes,

1. what you can do is get a mil eliminator that you can wire into the 02 sensor

OR

2. What you do is go to the auto parts store pepboys/autozone or where ever and get 2 spark plug non foulers 18mm, ask for them if you can't find them.
Then what you do is drill one out all the way through so you can screw your 02 sensor into it you will need a pretty thick drill bit. once you do that screw them together and screw them into your 02 sensor bung on the exhaust and then screw the 02 sensor into them.

What this does is take the 02 sensor out of the exhaust so it is not reading as much raw fumes as if it was in the exhaust itself.

My friend with a GTI and myself have done this and we have not had our cat codes return.

I think i will have to give that 2nd one a try, if i can get my o2 sensor off...which is stripped to heck from previous owner....

 

[ruskeyjdm]

"Basically the First o2 Sensor that is Pre-Cat is what Speaks to the ECU.

The Second o2 sensor is what the non-fouler is installed on when a header is installed. Installing a header removes the first Cat. The 2nd o2 sensor does only 1 thing, Verrify that Cat 1 is working.

Your corect The non-fouler creats a chamber outside the direct exhaust flow reducing the emmisions it receives, tricking the o2 sensor into thinking the Cat is there & working. It send back a good reading and all is well.

All in the while o2 sensor 1 is comunicating with the ECU as if the 1st Cat is still there"

ok i did a little searching about the non fouler set up and i just want to get this straight.
I do the non fouler on the o2 sensor that is hooked up to the manifold?
Im confused at which of the sensors is making the CEL go off? the one on the midpipe with no cats or the one on the manifold??

 

[MSP #167]

the downstream 02 sensor gets the non fouler

 

[ruskeyjdm]

ok thanks man, just looking at the pics of that guys aftermarket headers....i got a little confused.
ill give it a try

 

[Neez]

man, if you guys are complaining about high gas prices.. come to saskatchewan or canada in general and see how you like it.. we are paying $1.50/L of premium fuel.. which is about 5.50/Gallon i believe. (check the math) haha.. its pretty bad, but nothing to stop me from driving my msp