wstrohm

I'm a bit concerned about the current fuel mileage on our '94 FD, and also about the unburned fuel smell from the exhaust when the engine is cold. Possibly the two conditions are related; or if anyone can point at a possible cause, I would appreciate comments. I've attached a plot of the mileage history of this car, the engine of which is very slightly modified, as shown in my signature. The car is driven mostly locally. Last time on a long trip, it returned about 22 mpg, but that was a couple of years ago. When coolant is cold, the temp sensor voltage reads about 2.33 volts at ECU terminal 3E, which is in spec, so I think the sensor is OK.

sc_frontier

iTrader: (3)

I'm guessing the low peaks represent cold months, where an exorbitant amount of fuel is used during warm up. When researching my geo metro, the guys with the best mileage use a block heater on cold mornings. Loss of compression could also cause your efficiency to decrease, as the rx8 has higher compression for better economy.

MazdaSpeedDan

iTrader: (4)

I would give anything for 22mph, I get like 10 for some crazy *** reason.

sc_frontier

iTrader: (3)

could be the the right foot fouling up your economy

MazdaSpeedDan

iTrader: (4)

I dont think so! lol. I drive in a military post 95% of my driving and barely even get into boost. Also might be my plunger...I was on E and I only filled up 14 gallons....so Maybe i have a smaller tank I dont know, that would be my luck.

FD3S2005

iTrader: (11)

man i feel like that lately, havent really filled up my car since i have no money since now im jobless.. maybe because i only put in 20 dollars at a time, it just seems like my gas gauge drops down faster than it used to, with normal driving.

gracer7-rx7

iTrader: (16)

How are plugs, wires, coils, air and fuel filter?
Has the trans and diff oil been changed?
Could reformulated fuel have an effect?
Status of fuel injectors?

JyRO

iTrader: (3)

Your mpg doesn't appear to be outside of the norm. The best I've done in mine was 24.XX mpg, and I was TRYING hard to get good mpg. It was a 750 mile trip 90% interstate, and going 70 mph or less on the interstate.

Around town ~ 19 mpg. I recently moved and now basically all of my driving is in town with as many pulls as I can find. I'd say I'll be doing good to hit 19 mpg now.

If I want mpg, I'll ride in my Corolla.


JyRO

FD3S2005

iTrader: (11)

i want another corolla, me and my ex friend bought the rusted rundown AE86, that worked fine and it cost around 15 bucks to fill up and lasted a week-week in half. Had to sell it tho. i would love to have a second car that gets excellent mileage, i could care less how it looks on the outside.

wstrohm

Agreed that it smells as if lots of fuel is being wasted at initial cold start, but this is Southern California, and today temperature is 82° F. (Just an example of typical winter temps in Orange County!) Weather is never really COLD here.

Current mileage on (original) engine: 105640. There are no stored ECU fault codes.

New (platinum) plugs and OEM plug wires at 90199 miles. Previous plug change at 84846 miles. Coils are original.
New Fram CA 6381 air filter at 98300 miles, previous change at 63256 miles.
Fuel filter changed at 63314 miles, not changed since.

Trans and diff oil changed at 102181 miles, previous change at 79800 miles.

Could be E10 fuel... always use Shell 91 octane ("V-Power").

Fuel injectors tested for coil resistance and activation voltage at 90199 miles (at that time replaced their O-rings and also the FPD). No apparent leaks at 42 psi pressure after re-installation.

nsk1

i've got a Honda Ruckus 50cc scooter for buzzin around town. i average about 90mpg and it offsets my less than ideal mpg in the 7 nicely. chicks dig it too.