Awhile back i got upwards of 25ish highway mileage....The reason i know and am so picky is becuase i drove back and forth to college and could easily notice a difference. After i installed the CAI and the Airfoil, I belive that it decreased? But these mods are supposed to increase if anything....? I know the car is still making good power, because while i was getting the bad gas milage after the mods a ran a 13.6......

I have done numerous steps recently to regain my former mileage to no avail. I thouroughly cleaned the TB, and installed new AC o2 sensors, i have full emissions sys. and replaced pcv valve, and many many types of fuel system cleaner and such. I have thouroghly checked for vaccum leaks and replaced many of the hoses...and leaks around the CAI......

Nothing works!!!!! I know get like 15-17 at the most with almost purely highway mileage, by the way this is an a4 with 2.73's for christ sake. What should i do???

 

could just be your imagination, or you are driving harder, what is actual gas mileage?

 

definetely not driving harder, this is almost purely highway milage...actual is 17.* last time i checked, but i know the car got at least 23-25 but it seems to be slowly getting worse, even after i changed o2's that had almost 90k on them!!!!, also cleaned TB which was very dirty, these things should have helped severely!!! whats wrong?

 

usually people that have these types of cars don't really pay attention to gas mileage, but if this helps, my 97 was a 2.73 car and i put 3.73's in and it didn't make much of a difference. i only dropped 2 or 3 mpg!

 

That is interesting..... Maybe, you are having some problems with the PCM????? Any codes or anything?

 

I seem to have lost quite a bit of mileage with my header and TC install. I need to check some things but I think I am around 15 MPG as well.
Not that it matters to me overmuch but I just wonder if the TC and gears (3.73s) will kill it that much. I need to run a tank and try to keep my foot out of it and see what I get.

 

The TC will decrease milage pretty bad, depending on what stall, a 2400 would'nt be bad, but a 2800 combined with 3.73's will be very very noticeable in gas milage, but if I had that combo i would'nt care anymore, because a stall in these cars really moves out.....

 

Does not bother me, not my daily driver.
I just wanted to make sure it was the gear/TC combo and not something else.

 

Try taking off the vac hose to the FPR at the intake, leave the other end connected to the FPR. Apply a vacuum to the hose and see if the FPR will hold a vacuum. I use a brake bleeder vacuum pump. You may have a hole in the FPR diaphragm. This would allow fuel to enter the vac hose and eventually end up in the intake and could account for your bad fuel mileage.

Also check the fittings at the fuel filter. Since they're quick connect style, they have been known to leak. Although doubtful since you would have seen a stain and also smelled fuel.

 

I assume FPR means (fuel pressure reg.) if so, can you tell me in a little easier terms what to do eactly?, The FPR that I have is a redish color and is large and mounted on the drivers side valve cover on the middle two bolts, is this stock? Because my friend told me that it was a holley regulator? But i honestly have no idea, it could be stock........so what exactly should I do to check this. I've checked the fuel filter hoses repeatedly after i recently changed the fuel filter a couple months ago.

 

a friend of mine just told me that it might be worthwhile to clean my MAF sensor? Is this safe to do? Is this worth a try? thanks

 

yeah, you can try cleaning your MAF, I used electronic contact cleaner. gas mileage went from 10 to 13 mpg city. I think I can squeak out 14mpg.

 

Alright, I just cleaned my MAF, it was pretty dirty. so I'am hoping taht will mix my problem. IF it does not, is it possible that my fuel injectors could be the problem? What possibilities do I have for those? Can they be serviced?, or do they just have to be replaced. Thanks all....

 

I don't know how much this will help BUT.... I always check my gas mileage and saw mine going down too. I also noticed that there was a squeak at idle in the engine bay after I put my CAI kit in. So I cut a hole one night in the cover below the filter but then I wrapped the bracket with electrical tape. And here's where I'm talking about the bracket which the CAI connected to the radiator support. Any way after that I got back about 4-6 mpg. So I think the timing was retarding from that squeak I had and my mileage went south. One heck of a coincidence if it wasn't from that. Good luck and listen to the engine bay.

 

Yeah definetely no squeaks/rattles from the engine bay. Nothing as freak as that, I of course checked for all the normal problems. Actually I already have that pannel cut like that, has been like that ever since the CAI install. Also, like I said, they car is making excellent power, 13.6 for my mods seems like its making more power than it should...ne wayz, but the gas mlg has gone to hell......ANY suggestions would be great...Thanks