Tech, or whomever may know:

I have been experiencing poor fuel economy over the past few months. I know that the fuel ressure regulator was bad. I had originally experienced long crank times in addition to the poor gas mileage. When I changed the fuel pressure regulator, the long crank times disappeared but, alas, the poor fuel economy has not gone away. Before I was getting about 20-21 in town and now Ican get anywhere as low at 17 in town but more like 18-19. The fuel pump was replaced due to an unrelated problem in June. The fuel filter was replaced in May and the air filter was replaced in March (about 10,000 miles on the air filter). Any ideas where to start from here?

Thanks for all your help in previous posts and for your anticipated assistance here.

 

When was last spark plug change?

 

Thanks for your response Tech.

Plugs were changed in April or Early May. I used Denso Iridiums. Incidentely, I had to change both of the coils at the same time that I changed the plugs.

One thing that I forgot to mention. I really hadn't considered it might change the mileage much, but here in this colder weather, we run the rear defrost almost continuously in addition to the AC with the highest fan setting. The AC is always on hot, but I am not sure if the draw from these devices will cause that much (2-3mpg) difference.

Thanks

 

It might take a little bit.
Did the gas milage drop after the plugs were installed?

 

No. If I remember correctly, the gas mileage actually went up, but very little. The only change that took place with the changing of the plugs and the coils is that the car was no longer misfiring.

I guess that I am at a lossfor what to try next. It couldn't be the injectors, could it? If so, how would I be able to tell? We haven't been changing the way that we drive at all, in addition, there are no drivability concerns, it seems to run just as strong as ever. By the way, what kind of decrease in gas mileage should one see for cold conditions?

Thanks for all of your help.

 

I doubt injectors.
Not sure how much you would loose with it being cold.

Do you gas up at the same place all the time?

 

hey all,

i was experiencing the sort of same thing with my car (again, a volvo s40 2.4i) but it's only still pretty new. i babied it for about the first thousand miles (right now it's at like 23000) except for the first day when i took it maybe 65, 70 max down a highway home from the dealership (it was like a 20 minute drive)

but my gas mileage is around 23-24 mpg--my last tank only gave me around 290 miles to what the manual says is a 16 (to be specific, 15.9) gallon tank. after i fill up, the max it says on my computer says 350 miles to empty tank when theoretically i should be getting around 400-450 miles from each full tank.

surprisingly enough i filled up last night with my trip computer saying there was only 40 miles left to empty tank, and i topped off at around 11-11.5 gallons.

does anyone know if i did anything wrong while breaking my car in? if i messed up the engine? and if the miles to empty tank number should increase as i break my car in even more?

 

I was getting 17-19 max mpg on my '00 S-40. I replaced the plugs w/ irridium plugs and a $70 K&M filter. I just did a 700 mile road trip and got 29.3 mpg over the entire trip! Mountain roads and some high rpm driving included ! If only freeway, I'm sure it would've been 30!