Engine/Transmission (1998.5 - 2002) Sudden drop in mileage!

[ESwartzer]

My engine starts well runs strong and idles very smoothly. My issue is that my mileage has dropped from a solid 22 and better on the freeway to around 17- 18 in the last several tank fulls. I know that its probably one or two of my sensors that could cause the issue, so I'm asking for advice on what to check and in what order to check them. Any help would be appreciated!

Thank's Earl

 

[NIsaacs]

Did you change tires or air pressure recently?



Nick

 

[MChrist]

Check your alignment, also. Look for uneven tire wear. Check for dragging brakes, too.

 

[Oasis-3]

Winter fuel ? maybe try some power services in your tank and see if it helps.

 

[magaliasram]

Probably has nothing to do with the price of tea in china but I have noticed a steady decrease from the 22 to 23 I was getting down to about the same since the introduction of low sulfer fuel. Additives seem to help some when added to every tank of fuel.

 

[John - K5AWO]

I would be sooooo happy to just get 17-18 mpg on the freeway. 22-23 ??

foggy dreams for my truck, 10 uphill and 14 downhill.

 

[ESwartzer]

No change in tires or air pressure.

 

[ESwartzer]

Isn't the map or IAT sensor responsible for the richness of the fuel mixture? That's where I'm sort of leaning as being the problem. In the central valley of Ca. I dont think we have winterized fuel, but if they did start carrying the stuff would it make that big of a difference in mileage? Again back to my first question, what sensor controls the fuel mixture, and how would I test it

 

[sfritts]

pull out your MAP sensor and IAT sensor and clean them with spray on carburetor cleaner. I have to do this about once a year on my 98. 5 when the milage drops. They get some carbon on they and in the hole in the MAP sensor.

 

[madmanmanick]

Is that what your actual fuel mileage is or is that what that crappy overhead display is telling you. I found that the mpg is off quite a bit sometimes. When I fill my tank I fill it right to the fuel cap every time. I then take the odometer reading, minus the previous odometer reading and divide by how much I put in. That is the only way to truly find out your mpg. I keep track of it in a green memo book that I keep in the center console. I have also noticed that my mpg gets better in the winter, then gets worse in the summer. One theory I have is that the cooler air in the winter is more dense and allows for more of it to go into the engine.

 

[CEdwards]

Most common cause is air filter, that alone makes the biggest difference. I used to think just because it looked clean and had no obvious dust that it was good but thats not really true. If your filter indicator even starts to show anything change it. It can make a big difference. I cleaned the iat once in a buddys truck and it made a 2 mile per gallon increase according to his display. I dont have a display and i've noticed that most people with one seem to think they get better mileage than they probably really do.

 

[ESwartzer]

I don't have an overhead display, everything is hand calculated. I top off my tank every time I fill up so that is not the issue. I will check my air filter though i generally clean it every few months