Drastic MPG Drop since . .

[mikey1981]

my new fuel pump was installed last week.

i got like 160 miles to the last tank. im about to get the same maybe even lower.

does this mean they are covering up a problem by increasing maybe the richness or whatever. I know my stuff, but not too well. There are some intell. car guys on here, id like an opinion of what they possibly could have done to help prevent the misfiring/detonation in the engine that would result with me getting 160 or less to a tank now.

 

[9Hooker]

here's what I'm thinking.. the only way the fuel pump would affect you would be if it increased fuel pressure and somehow the fuel pressure regulator is not doing it's job. did they do anything else?

 

[erhayes]

In addition to 9Hooker said; maybe measuring over one tank is not enough to say mileage is down. What makes you think you're engine is misfiring or has detonation issues? do you feel the ignition cuting back by a step loss in power or a missing by feel or throwing a code?

 

[mikey1981]

erhayes, without reiterating many many posts ive made about the issues my car has had, the misfiring is fixed with this new fuel pump. the last 2 tanks of gas have given me 160 miles since the new fuel pump and misfiring issues. i was routinely getting 280+ 90% city driving.

 

[Mazda3]

Mike did you get the latest PCM and TCM reflashes?

 

[mikey1981]

yea, my car is actually up to date on every one of them

my MPG has varied here n there, but not by 100+ mpg that is just strange.

 

[CXRabbit]

Mikey,

I hope they can figure it out for you... I will tell you, my husbands car (not a Mazda) has suddenly started using WAY more gas (he's down to like 12-14 MPG on a car that should be getting 26-32) and no one can figure out what's wrong (so far).

 

[mikey1981]

maybe its just a bad batch of gas that made its way into the east coast, ..u never know.

im on my 3rd tank. . . if this one does the same thing, and now the weather is in the 50's, it will go in.

 

[Mazdaspeedgirl]

FWIW my 04 RX-8's gas milage plummeted to 12/16 when they did some reflashes. My opinion now is "if it ain't broke, don't fix it"