Horrible MPG!!! [Archive] - Audi Forums

: Horrible MPG!!!

02-27-2011, 08:36 PM
I have an '01 S4 that recently went from getting 22mpg to 16.6mpg:(...and NO, its not because i am racing around town, in fact, i am driving like a grandma in hopes to get over 17mpg. I know this is a broad question, but what could be the culprit for this sudden decrease?? I filled the antifreeze (that was below the minimum line) like a week ago but it has not gone down since. That is the only thing that is out of the ordinary, everything is running like usual and i dont have a loss of power (although i haven't really tested it, remember, grandma driving...). I have APR's software but i have had it for around a year without any problems. Any feedback would be greatly appreciated!!!

02-28-2011, 02:07 AM
First of all you should run a VAG-COM test on your car and check for error codes. Very low MPG can be cause by a bad lambda sensor or by a bad MAF. The problem is that you see the error code only when the lambda or MAF ar totally broken, if they are close to dieing VAG won't report anything.

03-06-2011, 05:33 PM
thank you sir, i will run over to my shop and have it hooked up real fast...should they be able to see if they're close to dieing or will i have to wait till their completely broke for anything to show up?

03-18-2011, 02:39 AM
There are ways to see if the MAF is close to dieing, I wrote everything here: https://www.audi-forums.com/b5-forum/58591-log-maf-strange-values.html#post174270
I explained how to do the MAF test step by step.
Also check the coils and spark plugs, they are not very expensive to replace but they are very important for the engine.
Good luck.