Hello everyone, my GF's 98 Civic LX recently had an 02 sensor go bad. I replaced it for her with a BOSCH one. used the Actron diag. tool and it said everything was good to go so I cleared the CEL code... she's reporting really poor gas mileage and this had started prior to the 02 sensor going bad. no more codes and car runs fine. any ideas on what could be causing this? I'm thinking the engine is running rich but not sure how to check that and not sure what would cause this.

I've tried searching the forums but my search for "poor gas mileage" or even just "mileage" didn't return any results.

any help would be appreciated.

Thanks.

 

thats funny, i found plenty of results under poor gas mileage. take a look at the spark plugs, that will tell you if your running rich. when was the last time you did a tune up? lots of things can contribute to bad mileage, like tire pressure.

 

last tuneup was 60k, car has close to 110k now. I looked at the plugs lastweek and looks to be normal. what should they look like? I will check tire pressure later tonight.

thx

 

last tune up? the car did have a timing belt/water pump change somewhere in between, no?

and he means by them being rich is they'll look scorched

 

the plugs looked like it had white powder on it. will replace them to be on the safe side. as far as timing belt and water pump, this has not been done yet. water pump, i think i might be able to manage but timing belt, I doubt I will be able to do... its my GF's car and I told her she should get it done instead of risking it going out. Most girls just drive cars, they don't have the love we share for them. how much should we be expecting for a timing belt job?

 

white usually means lean. simply changing spark plugs won't fix that. have your timing checked

 

iono how much it is to change it, I've written up like 5 bills in my entire life (and one was for an engine swap...) .. in any event, I don't know how much they'll charge in labor, usually it's just the price of the belt, which is like 30-60 from a parts store, not expensive, a lot less expensive than u'll pay if it snaps...get that done ASAP, it's pretty important

and poster up above me is what I'd say, listen to what he said, might wanna check ur a/f ratio

 

If your last tune up was almost 50k ago, you should definetely buy a timing belt kit(timing belt, tensioner, water pump), change air filter, new plugs and wires, check tire psi, oil change, maybe even fuel filter and pcv valve to be on safe side. If it's your timing causing your motor to run lean hopefully it will be corrected after you put the new timing belt on. But if you do all this it's a pretty good tune up, should see a drastic change in gas mileage. Good luck