When was last time the fuel filter and regulator was changed?My 2001 m3 has a misfire with no codes thrown, I notice increased fuel consumption and a rough start-up idle at times. I am original owner, the car has 200K plus on odometer, no intake leaks (confirmed with smoke test), throttle bodies cleaned as well as the idle control valve, vanos done, recent new plugs, fuel filter, fuel pump and air filter. Car has original MAF and pre/post O2 sensors (I plan to change pre O2 sensors soon).
In looking at the fuel trims I see negative trim values as follows LTB1 -5.4 and LTB2 - 3.9 on average which improve ny a few points with car at WOT and hot, but do not get to zero.
I tested the fuel pressure today and found some results that I am trying to understand as follows.
With fuel pressure gauge hooked up, turn key and get an initial pressure reading of 73 psi which is just within spec. but then in 5 seconds drops down to 62psi (with multiple runs to confirm).
Start car and the PSI jumps back up to 70 PSI then oscillates back and forth from 73-68 PSI with engine surging in attempt to find stable idle.
In about 10 seconds the engine idle starts to run smooth and the pressure stays at 62psi engine running (not in spec).
Shut car down and the pressure goes down to 58 psi immediately.
Over the next 30 minutes the pressure drops down to zero - will not hold pressure.
Hoping for some help in confirming that these symptoms indicate a failed fuel pressure regulator and that it also is likely the cause of the misfire and perhaps the negative trims.
Any words are greatly appreciated.