help with bad gas mileage, 98 EX!

[cypress98]

Hi, I'm a noob, sorry for the low-brow questions. My girl just bought a Cypress Green 98 EX Coupe with 50K miles here in Mexico. We are working on making this wonderful car cool and tight but there are several difficult questions... I'll post them on separate threads, if that's OK-

First: Very bad gas mileage! We drive in Mexico City with very high altitude (7000 feet) but the mileage still sux, about 20-25mpg in spite of recent dealership total tune-up. What should we check for trouble? Sensors, modules, etc? Scan the computer?

I suppose we could get +30 mpg at this altitude on moderately hard driving. The engine runs and performs very well. What is wrong???

BTW, there might be an answer to all those threads for whining, whirring, squealing engine noises... our car had a bad case when purchased... it was a damaged tensor pulley unit, had the whole thing replaced at dealership for US$80 and noise was gone.

:cypress

[SlowerCivic]

It might have a bigger engine in it.I thought the EX models usually did but im not sure.I dont really know what you can do for better gas mileage.If you lighten the weight of the car it would get better gas mileage cause it wont work as hard but I dont know if the difference would be noticeable.You could take out the back seats,spare tire,cut the well where the spare tire was and get sheet metal welded up there but it make sure its thick.You could also get polycarbonate sheets and cut them in the form of your windows.really theres no explanation for that kinda gas mileage unless you were trying to increase it with a bigger fuel pressure regulator or Fuel Management Unit,maybe the car had bigger injectors put in it.

[cypress98]

Hi!:
Well, no, its the original D16 SOHC engine on this Civic. High altitude accounts for lower gas mileage but I still am way under expectations.

I dont know if the previous 2 owners did any mods but as far as i know they were working ladies and the car seems completely original. I was thinking maybe some sensors or modules are bad and might have been skipped at the regular dealership tune-up. Might there be some kind of error code in the ECU that can only be seen by scanner? Do dealerships scan at tune-ups?

Any help highly appreciated...

[cypress98]

HELP!!!
OK, here's a thread on the issue:
http://www.automotivehelper.com/topic178206.htm

Now, is any of this applicable to a 98 EX Civic??? Is there a vacuum system? How do you reset the ECU??

Help
cypress:

[blitzcivic]

well i had a similer problem i was getting bad fuel econ. so what i did was check my fuel pressure and it was stuck on 55psi even when i hit the throttle so i test my fuel pressure regulator with a vac. gage and it was stuck. so i replaced it and problem was solved

[cypress98]

Thanks for your advice! That could be the problem... uuuh, where is the fuel pressure regulator located?? I know, I have to buy the service manual... but for now...