I have a 2001 VW Jetta 1.8T. About 6-7 months ago, it stopped running. It would crank up and drive once per day, but after that it wouldn’t start until you let it rest for another 10-12 hours at least. While running, though, it went fine and I could drive it for hours. As soon as it stopped, though, wouldn’t start again. I took it to the mechanic I usually go to, he kept it for a few weeks and finally came to the conclusion it was the computer. So I took it to the only guy I could find who could work with VW computers in town, we got a new one, and it still didn’t work. He then told me it may have to go to the dealership to be completely flashed. I had it towed there, and it’s about an hour and a half away so it was quite a tow, and after a couple days they call and inform me that, no, the computer is fine, but that the Mass Air Flow Sensor and spark plugs had gone out. I had the Mass Air Flow Sensor changed about a year before, and it was still under warranty, so I was skeptical. I asked them to go ahead and flash the computer and put it on, which they did begrudgingly, constantly telling me that it wouldn’t fix it and that they see no point in it, but I figured it was there, and I could always switch to the old one, so I might as well have it done. They change it out, and now the car won’t start at all. Not even once per day. So we hitch a trailer up to a friend’s truck and haul it back (my friend’s engine AND the trailer broke on the way, just to further inform you of the curse of this car). We bring it back to town, back to the mechanic, and he takes a look at it. He puts a good Mass Air Flow Sensor in it, won’t start. Puts the old computer back on there, starts, but won’t again for the rest of the day. Puts the Mass Air Flow Sensor from my car onto another Jetta, turns on, runs fine. Replaces spark plugs, same thing. So now we’re back to square one. We still kind of think it’s the computer, but the dealership keeps saying that they flashed that computer and that it can’t be the computer and unfortunately they’re the only place within a reasonable distance with the ability to work on these. If anyone has any ideas on this, I’d appreciate any help at all. Thanks.
What about leaving it w/ the dealer and asking them to solve the mystery? The fact that it runs w/ one computer and not w/ the other may indicate that there is a problem w/ the replacement–where did you get it?
Otherwise make sure your insurance is paid up, put the “good” computer back in, then leave it in a questionable neighborhood 
If it starts once per day, I’m thinking drive it to the dealer, park it, prove it is a no start, and then let them diagnose from there. Provide a list of all items done so far, so that they don’t unnecessarily duplicate that work.
Could be a fuel pump problem, was the pump checked?
They agreed it would not start, but would not agree it was the computer. When tested, it actually gives them a reading that it’s fine. The first mechanic got a reading that the crankshaft sensor was going out. He replaced it, tested fine afterwards but still did the same thing.
Assuming they checked it while checking the mass air flow sensor. They said the gas was running too rich, which would be a symptom of the sensor.
My friend had a similar problem with her 2000 Cabrio. It was a bad relay for the computer.
Really, the dealer needs to have this car for a couple of days and experience the problem first hand.
I’m just weary of bringing it back to them because they wanted to charge me over 1500 dollars to fix something that it turned out was not broken.
No start? what kind of no start? Does it turn over, or nothing at all? I had a little Jetta that wouldnt restart and turns out the starter would get hot and not work unless someone tapped (whapped, really) it with a hammer while someone else turned the key switch. It really brought my little family together, and made my children feel very important. And they were! Couldn’t make groceries w/o them! Anyway, went through 2 starters with that car. Same problem with each. Great little car otherwise.