Fuel pressure spec is 31 psi, rising to as much as 41 psi with the vacuum hose removed and plugged from the pressure regulator. If there's no symptom in the first three gears, this suggests the cause is load-related. It's very rare to solve a running problem on a Chrysler product by replacing the fuel filter, however, there are problems with the pickup screen in the tank collapsing and blocking fuel flow, but that usually occurs when the largest volume of fuel needs to flow, which is during coasting.
The MAP sensor responds to load and would be a good place to start. First check the other hoses for vacuum leaks. You can watch the signal readings on a scanner too, but very tiny changes that we can't discern result in big changes in the fuel metering calculations, so it's hard to tell what's normal and what's suspect. The Engine Computer will accept any voltage reading between roughly 0.5 and 4.5 volts, even if it's wrong, The voltage has to be really wrong to go outside that range. That's what sets a diagnostic fault code.
Have you checked yet for diagnostic fault codes?
This reminds me of an intermittent problem I chased on my '88 Grand Caravan for a year and a half until it finally failed completely. It acted exactly like a dead accelerator pump in a carburetor, but only on real hot days, and then only at anything above 1/4 throttle. Turned out to be a failing ignition coil. My guess is higher spark voltage was needed under higher load, and the coil was breaking down internally or arcing internally at those higher voltages.
Tuesday, July 28th, 2015 AT 1:57 AM