BootsElectric

I own a 2003 A6 Quattro (3.0) and I'm having what I'd guess to be a fuel feed problem. It all started about a year ago when I went to replace one of the brake lights, only to turn the car on and have it go absolutely haywire (the previous owner had put generic bulbs off the wrong wattage into the car). I was getting all sorts of flashing lights, the car wasn't running right, and nothing electrical was working. I obviously turned the car off immediately, and took the bulb out and replaced the whole set, and it ran almost normally. Ever since that point though, I had numerous issues with the car, mostly being intermittent idling issues and power issues. I ended up replacing the MAF, which made a HUGE difference, but I still have some lingering issues and I'm hoping for some help to narrow it down. One of my biggest issues is a total loss of power every once and a while. It's always towards the beginning of a drive, and it's normally going into a hill. No matter how much I press the accelerator, the revs will not increase, and the car will not shift. Next problem is that on start up, i will have severe idling problems (fluctuating from about 1500 down to 500), which will go away as soon as I start giving the car gas. I've also noticed a bit of a stutter when either driving at speed or beginning to accelerate, which jerks the car a bit. This doesn't happen often, and is pretty sudden. Overall, I've also noticed a lack of power in the car from when the light incident first happened. From what I've gathered, it seems like my issue is pretty much a fuel feed issue. I've noticed that my coolant gauge doesn't read anything anymore, so my first step is to replace the coolant sensor, but I'm wondering if the coolant temperature plays into the fuel mixture at all. If not, what are some other things I should go about checking? (As of my last read, I don't get any OBD codes). Thanks for any help!!
TL;DR I'm having what I'm guessing to be fuel feed issues. No OBD codes show up, and I've replaced the MAF. Looking for help on what to look at replacing/fixing next

georgeb944

Buy, borrow or steal a full VCDS cable and run a complete scan of all the codes. Report back here. You should also monitor the coolant temp signal. Yes, it does affect the fuel delivery to the engine.

Yes, it is fairly expensive, but throwing parts at the car without a clue is the most expensive method of diagnosis known to man.

jcman

Replace the CTS, a cheap part that don't last forever if your not in a position to invest in VCDS/Vagcom at least start here.

As far as the light bulb electrical issue something don't add up, did you replace the brake light bulb because of a dash indicator warning or the light burned out? And previous to the replacing the bulb "when it worked" did you see a dash indicator or nothing?? Only one dual filament type bulb will fit in the brake light socket with all brands being the same wattage, sounds to me like an electrical problem not a bulb problem........Yes, this is when VCDS can really help.