So I've got a 1999 A6 quattro which has been very well maintained over its 130k odd miles. This year it failed inspection because of 2 broken coil springs (inconveniently located on the front and back, necessitating changing all 4 springs) and a leak in the flex link of the muffler. Mind you, this isn't my usual garage - my usual was all booked up and I needed to get this inspection done.

These guys seem up to the job, however, and are nice enough. I replace the struts and muffler while I'm at it.

The day after I get the car back, engine light comes on - it's throwing oxygen sensor failure codes. Then the brake warning comes on - funny that my brakes should be low right after I've had the car inspected AND basically replaced my entire suspension. I'm suspicious that something was damaged with the muffler, so I take it back to the same guys.

They claim the oxygen sensor is dead - just coincidence. They don't have a great explanation for why my brakes are suddenly low. Whatever, just fix it please.

So they fix it alright - replaced an oxygen sensor and both front rotors (wtf? I thought we were gonna replace the pads?!). Oh well, at least the check engine light is off.

So, the very next morning (once the car has cooled down) - the car is hesitating from stop right after turning on. It's never done that before. Even when the oxygen sensor was "broken," the engine was always very, very smooth and consistent from start to stop. Push on the pedal, nothing happens for a second, then you hear the engine gurgle, then it suddenly tries to catch up with a *thwack* of power. All of this improves with warm-up, but doesn't go away completely. If I'm accelerating on the highway, it'll upshift with another *thwack* like someone just kicked the rear of the car. No engine light, but definitely not good.

So, please give me some ammunition to take back to this garage. If I'm getting screwed I need to confront those guys, and for that I need to know if they are reasonably to blame. The timing is just too much to ignore, but do you think the sensor is to blame? Poor quality, wrong type? Why would the car drive fine with a "broken" sensor, then drive like crap when its "fixed"?

Thanks any/everyone.

 

Of course this is so subjective - so I have to take your experience as accurate and can offer the following...

The initial work you authorized shouldn't have had them doing anything in/around the engine that would have caused the O2 sensor fault. That said, if the O2 was failing, it can cause the engine to trim fuel to compensate and then when it's replaced (and the signal is correct) it may take a while for the adaptive fuel trim to return to "normal". Time would tend to help this so you should know soon enough.

As for the brakes - again, don't know the "how" but it is pretty normal to replace rotors with pads on modern cars. Rotors just don't have the "meat' they had years ago to be able to be machined once. And with pads getting harder compounds (ceramic / metallic) rotors do take a beating and get sacrificed. So I can't say how your brakes suddenly went bad, but it's not unusual they would do the rotors (however, I would think this should have been explained to you up front).

The shifting...I haven't a clue.

Steve

 

Thanks for the response. It turns out that the mechanic forgot to tighten the connection to the mass air flow sensor, therefore the sensor was giving off erroneous readings to the engine.

Obviously they didn't charge me to for fixing their mistake, and they were honest about it, but I don't think I'll be back.