Hi, I have a 1999 VW New Beetle with 5 speed manual transmission and a 2.0 liter engine. Today I had the oil changed and since it was a little warm in Phoenix today, I kept the windows rolled up and turned on the AC. Was driving going 55 and the car died. I couldn't down shift to keep her going. She completely died. Turned off the AC and stopped, then turned the key and she started right up and kept going. This has happened before, but not all winter. During the summer, when the AC is on, this has happened. I do try to keep the gas tank full, because it seems that the only time this happens is when the gas tank is less than 1/2 tank. Today it was at about 1/3 tank. So the three things today was that it was 84 degrees, the AC was on, and the gas tank was at 1/3 tank. Any thoughts?
You're going to have to monitor the fuel pressure while this is happening to see if there are any irregularities.
Intermittent stalling and restarts is one of the hardest drive-ability concerns to troubleshoot. You would need to be monitoring and recording ignition signals, fuel injection signals, fuel system pressure, data bus, and scan tool info to paint a picture of what the problem could be at the time of the stall. Finding out what quits is the key to figuring out a diagnostic path to solving the issue. Some of these things that can cause a stall only occur for a fraction of a second. If you know for a fact this only occurs with the ac system running, that could be important information to someone troubleshooting your issue.
Even the most experienced techs can rip their hair out figuring out something like that unless it is utterly obvious.