Lower engine vacuum would result in higher fuel pressure, a rich mixture, and black smoke from the tail pipe. There's two forces acting on a molecule of fuel waiting at the injector nozzle. Think of a person about to jump out of a perfectly good airplane. There's two forces acting on them, the vacuum pulling them out and the guy behind them pushing them out. In the car, there's intake manifold vacuum on one side and fuel pressure on the other side. During coasting, vacuum goes way up. That would pull in more fuel causing a rich condition. To counteract that, fuel pressure is dropped so the net difference in the two forces remains constant. That's why there's a vacuum hose going to the pressure regulator.
A lot of the higher-class New Yorkers had automatic temperature control HVAC systems. I never got very familiar with their operation. I do know there are times when the mode will change on its own but that's the best I can tell you. When I ordered out the last of the '93 Dynastys, I ordered every option possible except the auto-temp system because I didn't want to have to worry about fixing it if something went wrong.
As for the stalling, I don't think you have a fuel pump or regulator problem. Unlike GM fuel pumps that commonly let you sit on the side of the highway, Chrysler pumps almost never stop once they're running. When the brushes in the motor become worn excessively, the motors fail to start up. A bang on the bottom of the gas tank often gets them going again for a few weeks, but once they're running, they keep running.
The pressure regulators seem to never fail. The only one I ever saw cause a problem on a Chrysler product was on a newly-delivered car that had a very long crank time to start the engine, but it ran fine once started. It simply had a cut five cent o-ring on it's nozzle that let fuel pressure bleed off as soon as the engine was stopped. GM has a lot of trouble with their regulators leaking fuel into the vacuum hose but I've never heard that about any other manufacturer.
The fuel filter isn't the cause either. They easily last the life of the car.
Here's something you might think about and compare your experience to mine. What HAS been known to happen is the pickup screen in the tank collapses or gets plugged with mud. The symptom is stalling when the highest volume of fuel is moved, which is during coasting. It takes a couple of minutes before the engine will restart. The faster you drive, the better the engine will run. I went to Minneapolis about eight years ago on the hottest day of summer. I noticed a slight hesitation when leaving a stop light; just enough to get my attention. About 30 miles later when I slowed down to turn onto a side road, the engine died and wouldn't restart. I plugged in a new MAP sensor; didn't help, but it did restart about five minutes later. Eventually I figured out it always died when coasting. Took me four hours to nurse it through the city again, then it ran fine at highway speed for 90 miles. It stalled again when I turned off the highway. The next day, the second hottest day of the year, it stalled four times in a 30 mile trip, then it was fine for the next six months. Finally it started acting up in the middle of winter. Had a couple of students look at it and they found the pickup screen plugged with a rust-colored mud. Threw in a used pump and it's been fine ever since.
Had I known what the cause of the stalling was, I could have plugged the vacuum hose going to the pressure regulator to nurse it through Minneapolis. By raising the fuel pressure, it's harder for the fuel to get through the regulator and go back to the tank, so a lower volume has to get through that screen. Because it couldn't pass that higher volume during coasting, the pressure was dropping too much and no fuel could spray from the injectors. We never did figure out why it started acting up in the really hot weather and was fine two days later when it was in the low 80s.
I overlooked this possibility because in your original post you said you already replaced the pump, but there are a lot of pumps out there that have to be installed into the original housing which means you would be reusing that pickup screen. If you got the entire assembly from the dealer or aftermarket supplier, it would have the new screen on it already.
Now that I know what caused my problem, if it were to happen again, I'd drive it with a fuel pressure gauge hooked under the wiper arm so I could see what happens to the pressure. If you have a pressure gauge, you might try that.
Thursday, August 25th, 2011 AT 11:39 PM