Originally Posted by torqls1

could u post a pic of the fresh air line?

Originally Posted by RPM WS6

Assuming his "315s" are 315/35/17, then there would be no reason to recalibrate. The overall diameter of those tires is only marginally taller than the stock size, and it would not make any noticeable difference (25.66" stock vs. 25.68" with the 315s).



Well, if you had filled the tank full before driving those 176 miles, and then refilled with 13.5 gallons, that equals 13mpg. This is a bit lower than what I would expect, given the information you have provided about the car's specs/mod level and your driving habits. I normally see about 14-15mpg (city) during the winter (and that's Chicago style city driving, which means excessive stop-and-go), but that's with an A4 car.

One thing that's not being taken into account is other habits you might have that would reduce MPGs, like extended warm-up/idling intervals or many short trips/several engine restarts. These are significant MPG killers.

At this point, having already done all the maintenance you've listed, there isn't too much else you can do, other than possibily chasing that intermittent rough idle. If you had access to a scanner, there would be things I would suggest looking at. You could also check certain sensors for proper operating parameters using a volt meter, but this requires a certain amount of knowledge to understand what the values indicate (not sure how familiar you would be with these readings). Additionally, this will only show you a portion of the picture, as there are several important values that can't be seen with a simple volt meter.

You could pull and inspect the new plugs, maybe one has a hairline crack causing the idle condition. Replacing the wires might be a good idea as well (or at least double check them for any deterioration or poor fitment), since you mentioned this hasn't been done yet. Double check all connection points that could introduce unmetered air into the mix, like the air bellow/MAF/throtte body connections; and if you want to go a step further, check any/all points that could introduce a vacuum leak (basically anything that connects to the intake, and the intake itself).

Front O2 sensors provide critical feedback for proper fuel mixture, and this is one thing you haven't replaced yet. They may not be working at optimum, even though you don't have a MIL/SES (yet).

Considering the amount of eletronics that are involved in the operation of a modern fuel injected engine, I would suggest investing in a scanner/software if you plan to diagnose driveability issues. You don't need anything super fancy, I'm using an AutoTap program from about 9-10 years ago that still works great for my personal and basic needs. Idle issues can be some of the hardest to track down (I've done my share), and without a scanner the only other option you have (once the basic checks are exhausted) is to start throwing parts at the car and hope for the best. This can get costly and frustrating real quick.

As for your gas gage, I too have seen that same condition (needle drops right after a cold start). I would not be alarmed by that, nor do I believe it has anything to do with your current issues.

Originally Posted by torqls1

when u say unmetered air if my lid isnt sitting completly flush like there is a small opening at the back of the lid it dosent sit flesh with the airfilter would this cause the mpg problem?

Originally Posted by RPM WS6

Unmetered air means any air that's entering the engine that did not pass through the MAF. The area you are talking about sounds like it's forward of the MAF, so it shouldn't cause any false readings.

I think the two sources of any missing MPG are your extended warm-up/idle times, and whatever is causing your rough idle.