I wonder if these problems are related. 3 times now I have gone to start my car (1st after parking for about 30 mins, 2nd after refueling, and 3rd after being parked all night) and the starter turns over but the engine will not start. The first time I took the key out after 5 mins and put it back in and it started. The second I was near a mechanic shop so we rolled it there and he checked fuel line, spark plugs and a few other things then tried to start it and it started (good guy, didn't charge me anything). The third time I took the key out and put it back in after 5 minutes and it started.

The second issue is that I've been tracking my gas mileage lately and when I was at half tank (after a fill-up), I had gone about 180 miles. Then after going down to Empty,I put 11.6 gallons and the odometer only read 306 miles driven. So I went from mid 30's mpg for the first half, then like20 mpg after that because the average was 26mpg. Something has to be wrong with that. My civic has 69K miles and is completely stock. Any suggestions on things to check would be appreciated. Thank guys/gals!

-Ale

 

have the battery and alternator checked.....
it could be from a weak battery... or corroded battery terminals.....

take off the battery terminals clean them and put them back on and then have the battery and alternator checked out..... free at most autozones, advance autoparts stores..... no need to remove them from the car. just drive the car up and let them hook up there wires from there machine to the car...

if your battery is weak it could make your alternator work alot harder which would put a load ont he motor all the time which can hurt your milage....

just a posible.....

if those both check out good i would sugest think about replacing fuel filter, drop in some fuel injector cleaner and maybe some seafoam thru the motor....

 

Is the CEL ON?

The start problem may be an intermittently faulty main relay, which controls circuits for both the fuel pump and fuel injectors.

I would not yet make any conclusions about gas mileage until you reproduce low mpg for a few tank fill ups.

 

regarding your gas mileage, i have always noted that the 1st half of the fuel guage took longer than the 2nd half. i really doubt that the gauge is perfectly calibrated b/w top and bottom half. it has been my experience. i normally measure mpg simply by the total number of miles driven divided by gallons when empty. i rarely measure when it's not empty.

 

i would have to say with the mpg issue that has to do with actually filling it up, when most people fill up thier car they fill till you cant even spit in it without losing some, that would be unmeasured gas, so it takes a little while for the gas to actually get down to where its being measured, thats you difference in fuel... so do what mundy said 2 or 3 times, and see how consistant it is... dont go by the guage

 

So I had the battery tested and it was bad so I've replaced that and have not had the same problem yet. As far as the gas mileage goes I'm still waiting, only down to half tank from the last fill-up. Thanks for the quick response. I frickin love my Civic though. I've only had trucks before, even the 26mpg is a huge improvement.

 

Hopefully the new battery will fix the starting problem. What is the CEL?

Does use of Cruise Control effect gas mileage? I also consistently drive at 80mph (on an automatic) on the freeway, do you know of anywhere to get information on RPMs (or speed) vs. gas mileage for year-specific civics? The gas mileage is still pending but looking the same but mundy5 and boostd92 made good points.

 

well the CEL means Check Engine Light.....

and if you keep it to 65-70mph you will get better milage... 34.9MPG from my 94s Z6 motor 5speed manual.
just depends on alot for your milage....... accelerate at a moderate/slow pace..... and coast to a stop. dont wait till the last second to let off the gas and right to the brake to stop at a normal red light or stop sign.

you might be suprised how these little things can make such a difference!
if i stomp the gas all the time and speed all the time on the highway my milage can easily drop to 25mpg or less depending how stupid i drive.LOL
hell even taking the highway cruising will get ya better milage than driving the same distance thru town..... when i do 1/2 highway and city driving home from work i typicaly get 32mpg from my 94 and 30mpg from my 99, 36mpg is the best i got with its automatic..

 

Fuel tanks are shaped weird and usually more fuel will fit into the top half than the bottom half, which is why the first “half” lasts longer.

Also, rpm is less of a factor in gas mileage than how far you are pushing down on the pedal.

EX – if you downshift while going down a hill your rpm may hit 4000ish, but if your foot isn’t even on the pedal, you will be using very little gas because there isn’t really a load on your engine.

But if you’re just driving on flat road your mileage is pretty much directly proportional to how much you press the pedal

Cruise control will often yield better mileage

Peak mileage also tends to be in the 55-60 mph range for smaller cars if you're maintaining a constant speed

I’m not sure how valid this is, but just from my experience it seems like all the civics from the original up to 2005 can get about the same mileage stock (somewhere mid 30’s), but again it heavily depends on your driving style and of course an auto will be less than a manual