Calling all S4 veterans. Can you please help me diagnose the problem?

**JayyyyyC** · 06-07-2008 08:19 PM

I won't be back until the 21st, but I wanted to get ready to start working on the car and getting it back into shape. I waited for a while, searching to see if there were others with the same symptoms, but I'm still not sure what's wrong with my car.

What I noticed that got me worrying about the car:
**Horrible gas mileage during part throttle (7.5mpg during normal NON-WOT acceleration from a stop, and ~13mpg during slow acceleration once adequate speed is reached) Before, I never saw gas mileage dip down below 10mpg during NORMAL acceleration, although I have seen 7mpg during WOT runs.

**Noticeable loss of power during acceleration compared to last month. Spooling noise has decreased and to get the same amount of power as I would when my car felt normal, I have to give it WAY more gas (and see ~6mpg when doing so)

**Car is very sensitive to gear changes - In other words, it seems as if everytime during shifts when you let the clutch out to engage a gear, the car has extra movement, sort of like swaying. I can't say if it feels like hesitation or not, but the car definitely does feel like it loses TONS of momentum. It feels like a bus when the driver changes gears. I'm no pro at shifting, but I know well enough that the car is definitely acting weird.

**NO LOSS OF COOLANT OR OIL. OIL LEVELS ARE PERFECT, COOLANT LEVEL IS PERFECT

**Readiness tests through my vag-tool show that almost all have failed. When I get back home I can list wehat has failed, but this is the first time I've noticed that things are failing. However, I was under the impression that it's just all emissions related, and doesn't affect performance.

Ever since I first noticed this problem (about 3 weeks ago) I have turtled the car, and shifted at no higher than 3k. I have gotten similar gas mileage as I did before when I used to do spirited driving on a daily basis. Something is definitely up

Your help will be greatly appreciated. Parts ready for the car when I get back:
Vast stg 3 clutch
Vast LWFW
SSAC TBE
FULL JHM drivetrain kit (SS, Linkage, bushing)
AWE DTS
034 Tranny + Diff mounts (street)

**mholme** · 06-07-2008 09:07 PM

I'll assume that since you have a VAG-COM you scanned for codes? Some of those symptoms(gas mileage) sound like EGT issues which won't always generate a check engine light and will richen your fuel mixture.

**JayyyyyC** · 06-08-2008 06:59 AM

I'll definitely look into that. I recall standing next to my trunk getting these out after a drive, and realized that standing a foot away from the exhuast nearly burned my leg hair off. I thought it was normal though for a turbo car to have such a hot exhaust after a drive.

Yea, and no CEL regarding the EGT sensor. I do have a CEL for the two primary o2 sensors (which will be addressed when I come back).

**highPSI-S4** · 06-08-2008 07:04 AM

Originally Posted by JayyyyyC

I'll definitely look into that. I recall standing next to my trunk getting these out after a drive, and realized that standing a foot away from the exhuast nearly burned my leg hair off. I thought it was normal though for a turbo car to have such a hot exhaust after a drive.

Yea, and no CEL regarding the EGT sensor. I do have a CEL for the two primary o2 sensors (which will be addressed when I come back).

Those primary o2's can affect your performance. To me it does sound emission's related. Also wouldn't hurt to check for boost leaks

**AudiSportB5S4** · 06-08-2008 07:30 AM

^^ yep, agree, the primary O2s will affect your performance... Rears will not, but the front ones sure will.

**JayyyyyC** · 06-08-2008 07:47 AM

Thanks. How bad did I mess my engine up ruynning fouled o2 sensors the whole time? (about 4 months). Or is it just a matter of running shitty and rich?

If compression tests aren't expensive, I should definitely get one done.