hello please help i have 2000 civic and it only get 14mpg right now, my mods are I/H/E (skunk2 intake), short air ram and apexi afc neo. So i just got the car last november and went straight to changing intake so i never know what was the fuel mpg originally was before modded it. Its been always 14 mpg after the intake change and even after i use afc neo it still got 14mpg. After i install afc neo the car cant rev above certain rpm and become very lean/rich that it cant even make compression, and then my engine shop said the ecu is broken broken, and it has already been fixed now the car runs normal and tuned, but it still got 14mpg. I have new iacv and maf sensor. Civic in my country dont come with o2 sensor. Is my ecu have other parts that are broken or what? i dont know what to do anymore i have read all thread about this problem but nothing helps. Or is this normal to get 14mpg with those mods?

 

Your civic has a MAF and no o2? What market are you in?

 

indonesian market, yes all d series engine here doesnt come with o2 sensor, i also got new tps too, no engine check before or after the ecu fixed.
update: the car used to be really hard to start when its cold, like when you unplug the injector and then start it for the first time, after it starts if i only give it a little throttle the car seems to run either very rich or lean and wont respond to gas and dropping the rpm to like 100 and then died, i need to throttle it to like 1600 rpm about 20-30% throttle maybe and hold it for like 30 secs to get the engine little bit warm and it could idle normally. The car just finished changing clutch today and it seems the unplugging and plugging sensors in changing clutch process helps fixing the cold start issues. Now the car starts easily in cold start and the engine aitomatically rev (to about 1200 like normal car) after it starts without i need to give it throttle and idles on about 300 when its cold.

 

What specific engine?

Why not use stock ECU?

Carbureted or PGM-FI? How does ECU manage fuel without an O2 sensor?

Auto or manual transmission?

 

its supposed to be d16y8 vtec in american marked, but its marked as f16y4 here, i use stock ecu its p2j ecu. Uhh i dont know bro maybe from maf sensor readings? its pgm-fi, why would a carburated engine use an ecu? o2 sensors in d16 engines are in the headers right?

 

The JDM P2J ECU looks for an O2 sensor. Looks like your "D16Y8" is actually more like the fuel efficient D16Y5 (Civic HX).

https://honda-tech.com/forums/honda-...-pics-2802636/

 

im sorry maybe its p2m then, i will check tomorrow, because im pretty sure d series in here doesnt have any o2 sensor, and i dont think it have jdm ecu, no high performance d series like jdm p08 head in civics here, all economical d series in civic.

 

http://www.phearable.net/information...daeculist.html

Does your engine have an EGR system?

 

Any way you can convert it to be a OBD2A or OBD2B? use all the parts as far as ECU, engine harness and 02 sensors from a 2000 USDM Civic D16Y8? maybe even the header/cat? make it a USDM conversion? Those after market parts never help with fuel economy it usually makes it worse, replace it all back to stock!

 

air filter
ignition system (as a whole)
cat converter clogged?
tires
tire pressure
driving habits

Check all the above.

-d16y4 is the non-vtec of the d16y7 here in usdm market.