Im getting bad gas mileage on my 94 sc400. About 11or12mpg.
I have done a tune up, only thing I havent done was replace the fuel filter which I will be doing when the oem filter arrives in the mail and I havent changed the caps and rotors.
But I doubt an fuel filter will change my mpg, car runs fine. Doesnt bog or anything so I do t know what the problem is. Even did the bfi to get more airflow thus getting better air/fuel ratio for better mpg and nothing. I dont do jackrabbit starts either so its deff the car.
Can I just take it to a dealer and they diagnose it or will they just feed me crap and try to get my car serviced and throw a lot of parts at it and drain my bank acc?
Thanks guys.

 

Yes dealer will drain you but what fuel are you running?

 

O2 sensors can give you really bad mileage.

 

I run only premium, either from bp, exxon, and shell.
And I have changed the o2 sensors, even though the old ones werent throwing any codes or dirty.
My exhaust smells rich, but it has always smelled riched and there isnt another sc around so I can compare.
So no-go on the dealer?

 

Ha, some awesome moderators we have on here...changing the title even though its more of a asking if a dealer can help me out thread than how to improve gas mileage thread, but w.e.

 

I have a similar problem. Started with bad gas mileage then hesitation and stalling started and now my TPS throws a code.

Also another thing that could be contributing to the problem is sometimes the brake pads get stuck to the rotors. All 4 of mine were stuck so I replaced the hardware kit and cleaned up the rotors.

 

There is very little the dealership can/will do that you cant do on your own, so why waste the money?

Plugs/wires/o2/cats/fuel and air filter/tire pressure/PCV valve/dirty MAF

^^Those are the primary culprits of bad MPG's. There are more things that can contribute, but those will be the most common. Another that is commonly overlooked, is a dirty throttle body that can be taken care of for less than $3 with some TB/Carb cleaner.

Another thing I would try along with the above, is Seafoam...it helps clean everything out you cant see. Start with those and see how things go..but dont waste $250 to have the dealer just look at your car and tell you the same things we are.

 

Is this a recent change or pretty much the way it has always been?
That does seem very low, assuming you are not on the car all the time.

 

Ok thanks, very informative! Only thing I havent done on your list it cats, fuel filter, and maf. Although I did use compressed air on the maf.

And its always been that way, when I first got it it was getting 10mpg then after o2s, plugs, wires, air filter, ect, pcv valve, and bfi it got to 12mpg lol and I dont let it idle much like some of my 4cyl friends lol. Only to warm up.

 

Any improvement with your MPG? I've got an o2 sensor popping up on mine which I plan to fix shortly after I get through a few other things. 12 is awfully low, but I seem to be getting just as much if not worse.

 

I get about 26mpg in my sc400 and the best improvement I did to help it was an adjustable fuel pressure regulator which allowed me to lean it way out as these run real rich in stock trim also it picked up a few hp as well.

 

Lets get a list of what you replaced, and what symptoms if any you are seeing

 

Let me know if you found out the culprit. I'm having similar issues and now mine takes forever to accelerate complete. Feel like granny starting out. Also, now when I hit about 65 the car shakes and feels loose. LMK

 

What adjustable fuel pressure regulator are you using? Very curious, trying to improve my mpg at all costs!

 

I have a walbro 255 fuel pump fuelab afpr with a -6an feed fro the rail to the regulator also I have an intake and axle back which might help just a tad bit.