check your statior output.
even though the tune up guide calls it high and low speeds its actually port and stbd bank.
lose 3 cylinders on one bank and its almost always a stator failure.
i was thinking it had something to do with spark it was only on cylinder and getting weak spark so i replaced the coil and the problem just got worse now the whole bank is out
testing is just to cheap easy and quick, before replacing a coil( rare rare failure) simply test coil primary voltage, but with a bank missing on a 3.1L motor its almost always stator related.
its a simple test with a peak reading meter.
