I have a crank fluctuation sensor that I havent been able to address yet,
and have been noticing that I am getting around 27 MPG. I dont drive hard or fast just normal.

Its a D16Y7 hatchback

thought surely this car would get 35+ MPG

does the cel put the ecu into some sort of safe mode with fuel maps that burn excessive fuel?

was gonan do the trick where you make the ecu see 4 volts also but not sure if you have to first unplug the sensor from the harness or if that even mattered

 

anyone?

 

27 as compared to 35+.. Fx it dood, not that bad..

 

I just wondered if a simple check engine light caused that?

 

Depends on what the light is on for. Some CELs affect mileage and performance, some don't.

 

Fix the CKF sensor circuit problem and gas mileage will almost surely improve. Most "simple" sensors provide critical ECU inputs required for determining optimal fuel trims.

 

Most D16Y engines I've seen with a CKF sensor fault will misfire constantly and barely run.

Fix the sensor, then ask questions later.

 

well i did the bypass the cel is gone but something strange occured during the bypass trick
its fixed which is good
I followed instruction per write up
the first part went fine

but when I got to the 2nd part something was up

when you are supposed to bridge c11 and c14

first i notcied that c11 was indeed a white wire with red stripe but c14 was a black wire with grey dots on it?
i also notcied that c12 NEXT to c11 was white
which is not the case in the provided picture
i didnt splice anything else

i turned car on and no cel
just by joining c 1 and c4 and clipping c1 lead out

not sure why the other part didnt match up
it is indeed obd2a
any ideas whats up?
and why did it work without me bridging the other 2?

 

ok so I had a code 54 Crank Fluctuation Sensor CEL when I bought the car
I did the bypass trick and the cel went away
I reset the ECU as directed

still getting bad gas mileage
I also notice that the car idles very low when warm
when the car is cold it idles about right
I adjusted the idle screw on the TB until I thought it was idled about right
was about 3 whole turns to get it up enough
to the point I could hear air sucking in

so Im still getting around 28-29 mpg
and sometimes it STILL idles really low after I adjusted the screw

it has no other mods than I/H/E

and NO cels currently

any advice on whats going on

whats the average MPG for a moderate to less aggressive driven civic dx

 

Related threads merged.

Are you getting 28 mpg from city or highway miles?

You may need to go through a couple tanks of gas before seeing an improvement in mpg, especially if you disconnected the battery or reset the ECU.

Also be aware that disabling the CKF sensor has eliminated the ability of your ECU to detect engine misfires and to throw misfire CEL codes. So, you could have misfires that you are unaware of.

When was your last ignition system tune up? Is the ignition timing set to spec?

 

stock mpg is 28/35, unless your driving all highway miles that sounds about right. im getting around 30mpg city/hwy mix. but again i shift under 2500rpm and put in neutral going down the hill. but always let it warm up 5-10mins warmer weather 10-15mins cold winter months. not worth few drops of fuel to wear out my engine in winter time.

 

Yes the engine does not no when to fire so It will go into close loop and just use pre-register data and just one cam angle sensor to fire. Fix the problem and then check it again. You cant start to do performance checks if your car is not performing right...... right?

 

1. Why did you half-*** it by "bypassing" the CKF sensor instead of repairing or replacing it? Do you normally do hack job repairs?

2. Did you run the idle learn procedure after resetting the ECM? '96-00 Civics are especially notorious for a low idle or stalling if the idle learn procedure isn't done after clearing all ECM data.

3. How did you adjust the base idle? Did you do it correctly by disconnecting the IAC valve while the engine was fully warmed up? What RPM did you set it to?

 

tard... all owners manuals say that you shouldn't "warm up" your car for extended periods of time as it increases wear, not decrease it.. In cold weather they say idle for 30 seconds and then drive lightly. Extended idling, especially on a cold engine is BAD FOR IT because those are always rich fuel mixtures and engines take longer to warm up via idling than when driven on. Nobody is suggesting hitting vtec after startup but to drive nice and easy until the engine is warmed up. You're wasting fuel and you're wearing out your engine more by idling your car for so long.

If you look in the owner's manual under maintenance schedule, cars that have extended periods of idle fall under "severe service" opposed to "normal service".

Another myth being constantly perpetuated by those who usually can't afford it to begin with.

 

That only applies to D16Y5 and D16Y8 engines with the M/T.. You do not disconnect the IAC valve on the Y5 with the CVT, the Y8 with A/T and the Y7 engines to set the idle.

 

i searched idle learn procedure and found nothing

would like to perform this correctly if can find info on how to do it

 

searched where? do you have the helms service manual for your model series car? If you have the helms, it's on page 11-221..

 

uhh thats on NEW cars. were talking 92-00 cars. letting them warm up Is better. pistons slap the crap out of the walls at 60+mph with cold ones. but you knew that. engines have an operating temp for a reason. and when its -8 degrees thats a long ways from 195 of optimal operating temps.

whats wrong is you tricked it instead of fixed it.

nuetral is a bigger gas waster then leaving it in gear btw.

does no one know how to use google?

 

I have been getting about 30mpg with no cel but my civic has 316000 miles

 

wrong thread much?

 

to the op: for what its worth i got better gas mileage in my 92si when i swapped a gsr motor than when i had the stock d16z6. like 5mpg better. my z6 was bone stock my gsr had skunk stg 2 cams header exhaust and a skunkmanifold.

 

So you got a new exhaust manifold? Was the old exhaust manifold a rusted pos?