Bad Gas Milage // Maintenance

[audimanstan]

Ive always experienced a rough idle since I bought the car (Audi A4 2007 Sline) in August 2016 and now I started to get some horrible gas milage and noticed some oil consumption! I did the following since purchasing the car...

replaced/changed...fuel filter, sparks plugs, ignition coils, cam follower, drop in KN filter, turbo inlet hose, vacuum pump, all fluids change, ran injector cleaner twice, snub mount, cleaned MAS...

Recently I noticed my gas milage shooting down sometimes im avg 12-15, wtf? (when I bought the car I was avg 25-30)

Car runs smooth but shakes on idle and on take off // No error codes

After doing some research I think it would be a good idea to replace the PCV?? Anything else I should look at?

ECS Assembly has PCV and Breather Tubes together....What is the advantage of replacing the Breather Tube?!?!?! Can I just clean if its dirty inside? (PCV Kit $166 / PCV only $40 )


All advice is welcome Please & Thank you

[deusilan]

Have you checked all of your hoses? Sounds like you could have a vacuum leak.

[hemantpd1]

Are you sure that your MAF is good. Bad MAF may lead to uneven idle and bad gas mileage.

[80sGuy]

Is the car modded?

[audimanstan]

Yes there are no vacuum leaks

- - - Updated - - -

Yes I checked by unplugging when the car is in idle and the car started to shake worst. So that's telling me the MAF is working

- - - Updated - - -

Unfortunately no mods lol

[Low and Behold]

After doing some research I think it would be a good idea to replace the PCV?? Anything else I should look at?

ECS Assembly has PCV and Breather Tubes together....What is the advantage of replacing the Breather Tube?!?!?! Can I just clean if its dirty inside? (PCV Kit $166 / PCV only $40 )


All advice is welcome Please & Thank you

The breather tube is part of the pcv system. If you can afford it change both so that you know everything's been updated.

You can take it off and inspect it. There's a check valve in it that should block air from going back into the crank case under boost



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[Theiceman]

how old are your o2 sensors , maybe its causing the car to run rich, but I suppose there would be a code..

[audimanstan]

The breather tube is part of the pcv system. If you can afford it change both so that you know everything's been updated.

You can take it off and inspect it. There's a check valve in it that should block air from going back into the crank case under boost



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Thank you very much!!!

[wding2000]

I have been fighting reduced MPG for a while (and oil consumption at the same time). After replacing VC (there is a crack) and N80, finally replacing PCV fixed it. Back up to 22 mpg city, and about 1 qt per 3K miles. Happy. I do have minor oil leak at oil cooler gasket and will replace it at next oil change - should reduce oil consumption further.

I did not replace breather tube, which was replaced by dealer under warranty 30K miles ago (along with PCV). This is why I only looked at PCV the last - thought it should be good for only 30K. But hell, no, it is stuck when I shake it. I would replace PCV in 30K, or any sign of low mpg the next time.

[Harriz801]

Ive always experienced a rough idle since I bought the car (Audi A4 2007 Sline) in August 2016 and now I started to get some horrible gas milage and noticed some oil consumption! I did the following since purchasing the car...

replaced/changed...fuel filter, sparks plugs, ignition coils, cam follower, drop in KN filter, turbo inlet hose, vacuum pump, all fluids change, ran injector cleaner twice, snub mount, cleaned MAS...

Recently I noticed my gas milage shooting down sometimes im avg 12-15, wtf? (when I bought the car I was avg 25-30)

Car runs smooth but shakes on idle and on take off // No error codes

After doing some research I think it would be a good idea to replace the PCV?? Anything else I should look at?

ECS Assembly has PCV and Breather Tubes together....What is the advantage of replacing the Breather Tube?!?!?! Can I just clean if its dirty inside? (PCV Kit $166 / PCV only $40 )


All advice is welcome Please & Thank you

First thing I would start looking into would be checking with dealer records to see if your car has been brought up to date with the latest recall on the PCV. If I remember right, there was a recall on the PCV and if yours hasn't been to the dealer to be changed out yet, that could save you some money and eliminate another potential contributor to your mileage issues. As others have stated, I would look into o2 sensors or a clogged catalytic converter. How many miles are on the car?

If your unfamiliar to the B7 A4, then you'll find with a little research around audizine that oil consumption is common with the 2.0 FSI (if that's the motor you have). Some experience in upwards of 1 quart per 1000 miles. What kind of oil consumption are you seeing and were you not seeing anything when you first purchased the car in August?