Got out to the Jeep today and hooked up the fuel pressure gauge. When I turned the ignition on, pump ran for the normal 2 seconds and the pressure came up to 43 PSI. Started the engine and it moved up to 48 PSI, the needle was vibrating between 46-50 really rapidly, but would even out when I brought the rpm's up. Eventually it seemed to steady at 48 PSI, which I'm assuming is normal pressure?
Had it idling for about 90 min's and in that whole time, only got one short period when the idle went bad (heard the IAC motor close again). Fuel PSI remained constant, so I think that system is OK?
Also noticed that no engine codes have been set since the last reset about 2 weeks ago, which seems strange?
Got my SCAN tool to finally view all the sensors too. Seems there's 2 modules, one is 24 and one is 209? My tool was reading from module 24 which could only see the TPS, but when I switched to 209, the other sensors became visible.
O2 waveform looked normal, varied between .2 and .8 Volts. Only thing I noticed is when I revved the engine and let it go back to idle, the output would go flat at .2 V for about 5 or so seconds, then start oscillating again.
Beyond that, I checked vac lines, sprayed gumout, wiggled wires, cleaned up main batt and other electrical connections, all to no avail. Intermittent problems are clearly the most difficult to fix!