I have a 93 civic auto. Over the last week i replaced my old muffler with a new oem one and changed the battery. When i averaged my gas milage at the pump my gas milage dropped form 28-32 (average) to 20.3 mpg
I was wondering if the battery and muffler impact it that much or do i have something else going wrong here?

 

holy sh*t, 8+ mpg loss, that is not a muffler. Check fuel filter, injectors, oil, tires. the battery has NOTHING to do with mpg, unless it is dead and your alternator needs more power to keep to car going. But since the battery is new, it should get better, if anything. A friend of mine replaced his OEM muffler with a racing tip, in other words not muffled. He gets the same, if not better mpg. Since your replaced with teh stock, or OEM, muffler that won't make the back pressure or anything different. It's something else. Injectors would be my first thought, battery effects them., a lil. Fuel filter would make your car run crappy and you would know that it was clogged up, but sometimes they wear so bad that the filters let fuel filter quicker, in other words worse mpg. Then oil, tires next. good luck, hope this helped.

 

the o2 sensor just went out on my car.....it gave me a 10+ mpg drop.

Check your plugs, see it they look rich. (after a tune-up)

 

Yeah that was what i was thinking. That the battery and muffler couldn't have done it. Guess it is time to start ripping the engine apart and find the cause (or use this as an excuse to do an engine swap)

 

If you want 2 do the swap, cool with me. Your engine is prolly fine. It could be like what me and the other guy is saying, a part or sensor is out. Go to autozone and check the o2 sensor, if you don't want to get under there and check and see if it's all clogged up with carbon deposits. See when was the last time you changed your fuel filter? injectors checked? Is there any symptoms of your car? like hard cranking, dying at stops, smoking, etc?

 

i just got the car as a gift for finishing my first year of college with a 3.8 from my cousin. I have driven it for 2 months and haven't done much. I am going to check the fuel filter/wires/injectors/spark plugs today

 

good luck with all that. MOST LIKELY, it isn't a the spark plugs. Test your injectors. But the fuel filter, you have to take apart, you can't just by a fuel filter test gauge, lol. While you have already pulled the filter out, just replace it with a fram brand or something, it will need it sooner or later. Might as well get it out the way. Remember to releive the back pressure on the filter, unscrewing your gas cap.

 

took your advice and installed new spark plugs, Fuel filter, changed the oil (only had about 2k miles on it) new injectos... (ouch to the piggy bank) hoping the gas milage jumps back up

 

you didnt check the o2 sensors ????

 

i had the same problem and took it to my garage. they replaced the O2 sensors, cleaned my injectors and changed the fuel filter.

Then good as new.

 

I will check it after i get an idea of this gas milage. If the drop presists here is my next to get list. 02 sensor, ignition wires, and tires.

 

make sure your charcoal canistor is hooked up, wehn i got my swap the forgot to hook it up i was gettin lik 17 miles per gallon, then i hooked it up and it went up to 28

 

really! I didn't know the canistor was that important.

 

what is a Charcoal canister?

 

Ya i have never hurd of that?? where is that located?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by djsire &raquo;</TD></TR><TR><TD CLASS="quote">make sure your charcoal canistor is hooked up, wehn i got my swap the forgot to hook it up i was gettin lik 17 miles per gallon, then i hooked it up and it went up to 28</TD></TR></TABLE>
the charcoal canister itself doesn't give you any real mpg increase. (+1mpg max)
It's used to trap fuel vapors when the fuel evaporates in the tank. It is the then vented into the intake manifold while you are cruising down the road.
Without the canister the fuel will evaporate into the atmosphere.
Without the valve the CEL will be on.

OP: where is your foot on the accelerator now that you have your new muffler? Driving with it close to the floor will decrease your mpg really quick.
You could have also knocked around the primary O2 well enough (if it was weak to begin with) and caused it to start going bad. This will make your mpg fall fast too.

 

i just filled up and got 29 mpg. So it must have been the fuel filter or injectors

 

i was gonna say, if the o2 sensors were goin bad dont you think itd throw a code? i just had that problem, codes p0131 and p0135, turned out one of the 4 wires on the primary o2 sensor was pretty much blown off/burned

 

good to hear about the mpg issue solved. Now you'll appreciate those extar miles now, lol. good luck the rest of the way

 

Well i got a new problem that formed. The car is running alot hotter. After about 50 miles it reaches a point where i am forced to stop and let it cool down. I checked the coolant levels and it is fine.

Would it be the radiator or the water pump or something else?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcrx7zoomzoom &raquo;</TD></TR><TR><TD CLASS="quote">Well i got a new problem that formed. The car is running alot hotter. After about 50 miles it reaches a point where i am forced to stop and let it cool down. I checked the coolant levels and it is fine.

Would it be the radiator or the water pump or something else?</TD></TR></TABLE>
I'd check the thermostat first, and head gasket second.

If the thermostat is indeed bad, replace it with an OEM Honda piece only. Aftermarket thermostats tend to be problematic.

 

How do you check that and the head gasket?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcrx7zoomzoom &raquo;</TD></TR><TR><TD CLASS="quote">How do you check that and the head gasket?</TD></TR></TABLE>

always wondered that too ...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by flatblkCR-X &raquo;</TD></TR><TR><TD CLASS="quote">

always wondered that too ...</TD></TR></TABLE>

dunno if im right, but to cheak thermastat, pull it out and check if its damaged in any way, then drop that sucker in hot water to check at what temp it opens...hell for that get a new one lol 10-15 bucks

the head gasket..is the car making coolant disappear, does oil look a bit "milky" (oil+coolant ...check compression..while you're at it take the rad cap off, if you see at least on bubble come-up while doing the compression test, then i feel sorry for you.

 

Can't really feel sorry for me. I got the car for free as a gift. I expect some stuff like this.