2005 Century poor mileage

[Buicklover]

I have owned (5) Century automobiles since 1999, all with 3.1 liter engines. Current auto is 2005 model and fuel mileage is at least 2-3 miles per gallon less than any of the others. I live in Louisiana and current auto was first titled in Nevada. Is it possible that the engine was built to meet emissions standards more stringent than Louisiana causing poor mileage and if so, how would I go about correcting the problem?

 

[2k2cse]

How many miles are on the car? Do you know when the plugs, wires, PCV valve and air filter were changed? What about the other regular maintenance like oil and trans fluid? What mileage are you currently getting? There are so many different factors that could cause such a difference in mileage. Even any extra weight in the car, driving styles, and worn parts..

 

[Buicklover]

This car has 96,000 miles on it, air filter, engine oil, transmission fluid were all changed @ 93,000. I don't know when the sparkplug wires were changed, but they are AC Delco so it is possible that they are the original wires. The engine never misses or misfires and in fact it seems that it runs quieter than any of the other Centurys that I have owned. The 2005 that I replaced when I bought this car had 205,000 miles on it at the time I sold it. Thanks for reminding me to replace the PCV valve and I'll do that today.

 

[Buicklover]

Oops, I forgot to tell you that the other cars all got 30+ MPG on the road and this one has never exceeded 27 MPG. I used all of these cars for traveling at work and the equipment that I carried in the trunk was the same except this one. I am now retired and probably carry 75 pounds less weight now.

 

[Buicklover]

Today I looked under the hood and the GM sticker says certified for sale in California.
Could the computer be re-programmed and increase MPG since I live in Louisiana?

 

[Buicklover]

By chance yesterday morning I had the hood up immediately after starting the engine. I found that the outside of the fuel pressure regulator valve? was saturated with gasoline. I checked it several times later in the day and it was always dry. I plan to have it replaced today and hopefully this will improve fuel mileage.

 

[journeyforce]

That might be the issue but if not that should still be replaced because when it gets colder it will not start easy(think flooded carb in the old days)

Is your torque convertor lockup working? If it is not locking up then that will cause lower mpgs. if working it will give an extra "shift" at 45mph that is the TCC(that "shift" tends to fool people into thinking the trans has an extra gear

Good luck

 

[ViM]

Personally, I would change the plugs and wires, that's to old for me.

 

[Buicklover]

This will be my last post on this problem. I had the fuel regulator replaced and made a quick round trip to Fort Worth, TX yesterday afternoon/night with the cruise set on 75 MPG, totaling 674 miles and used 21.288 gallons of fuel. This computes to 31.66 MPG. I can live with that, and if I had driven more slowly the fuel consumption would have been even less. I'll plan to have it tuned-up at 100,000 miles.

 

[2k2cse]

That seems like reasonable mileage. I think you have figured out your problem. A change of plug wires might help you gain a couple more MPG if they're still the originals.

 

[BU TECH]

Good post! I'm gonna have to look into this, I haven't hit 30mpg in mine in a long time, been running mid 20's now.


I do have a bunch of other little electrical problems to look into as well, one i'm sure is affecting mpg.

 

[13aceofspades13]

another thing i have noticed with the 3.1 is there are a lot of little vacuum hoses, PCV, Evap, EGR, sometimes one of the hoses will be loose too, but its probably your plugs and wires...