First, my 99 max sat for a year after a friend helped me redo everything but the engine. I drove it about 3 months, and then it sat in a field for another 3.5 years and only got started a couple times. So it is falling apart, nothing I can do about that. I have been limping it along for a year.

#1 So I got in my car about a week ago, and out of the blue, within a mile of my house, the temp gauge is just below the warning line. I don't think it is actually overheated. It goes up too fast for one, but it also smells fine, runs fine, it doesn't feel abnormally hot under the hood even after 10 miles or more. But it worries me that the gauge does fluctuate, seemingly going lower (maybe in my head) when on the highway or if its raining. Antifreeze is 100% on a 4 month old radiator, so aside from a blockage or flow failure of some kind it seems far fetched.

#2 Then I see my gas gauge... it was climbing from 1/3rd, and eventually stopped at 7/8ths where it now goes to instantly upon startup.

#3 Then my car starts randomly dying at lights. Mind you it was doing this RARELY before, usually when its really cold.... which also caused sputtering takeoffs---which I'm assuming is the fuel pump going out. I was also having issues with pulsing idle RPMs and abnormally high idle on startup, probably the IACV from what I read. But that also stopped with the cold weather. But now, when you stick the clutch in the tach drops to absolute 0 instantly. This part can be remedied by keeping the defrost button or the AC on 24/7 to raise the idle RPM.

#4 Next, I try the cruise control, and the gas is PULSING. It speeds up a couple mph, then slows down, then speeds up.... very erratic. A few days later I show this to a friend and the cruise control shuts off after about 10 seconds, and the CC light steady blinks to infinity. My CC used to shut off when I would hit the blinker, and even to this day since it started working right, the CC light blinks a few times every time you touch the brake or clutch---even if CC isn't on.

So, my main thought would be a short in the CC module. Or maybe the clutch switch? Maybe the blinker switch? I haven't tried anything yet since I am just so done with both my cars (got a pristine 2006 A4 with a brand new turbo and timing chain, and the idiots must've done something janky, since the coolant flange started leaking 300 miles later). Has anyone had any similar issues on their max? Any ideas? Can I pull a relay somewhere and shut off the CC module without disabling half the car? I mean, only half the car runs at this point---the AC quit a month after I got it back, the power steering is mostly useless, and a rear caliper leaks so the rear brakes don't really work either. So I don't know if I can afford to lose the other half of the car, lol.

Any help would be greatly appreciated. I just need to limp this thing a little longer until I can put in the Audi's coolant flange kit.

 

Just to clarify this story. Your car sat for 3.5 years and you've been driving it around for about a year after it sat for so long correct?

Anyway, first thing I would do is check for codes and see what comes up. Sounds like you have a bunch of different issues going on here, from engine to electrical.

 

sounds to me like the vehicle speed sensor or a short in the dash behind the instrument panel
the soldering on the circuit board sometimes gets cracked

 

The one thing thats important with a car that's been sitting over a year check the fluids and leaks and the hoses and the harness wires since your car was sitting in the yard with grass and all the wild mother natures creatures can attack the car and the harness like rats ect.

 

If it sat out in the grass then yah just like Vqmaxman said, creatures can do all kinds of stuff....chewing on wires, creating a nest, also out in the elements doesn't help that too. Could be loose/shorted out wires somewhere. I'd check that. Electrical problems can create all kinds of weird issues.