My 86 745T stubles/stalls for short (1-2 second) periods, but never quits running. During "between stall intervals" the engine runs fine. These incidents are almost constant, occuring randomly but frequently (intervals between range from 2-10 seconds). It's worse on acceleration, when it feels as if the timing retards suddenly. It runs like this all the time. It also requires longer periods of cranking after sitting overnight or on an incline(i.e. driveway) which seems like it simply has to wait to get fuel (newer symptom; odd for an electric fuel pump design).

Since this began, I've done plugs/wires/rotor/cap, replaced the fuel filter and the in-tank fuel pump. I did a fuel pressure test (remained fairly constant at about 36 PSI and double-checked all the vacuum hoses (all are less than 3 years old). Interesting side note, this problem first cropped up 2 months ago--that's when I did the tune-up/pre-pump/filter/pressure testing. It stopped the stumble, but lacked pep and continued to get 15 mpg (down from 20 or so). Now the stumble has returned.

The Haynes manual says the FT is supposed to maintain 42psi, but the F is supposed to maintain 36psi. Could the previous owner have installed the wrong pump? If so, would this explain my symptoms? Is is possible for a fuel pump to "get tired"? I really don't want to buy the pump unless I'm sure it's the problem.

Any other ideas?