[s-cars] Running on 4 cylinders

[John Tilden]

Mike writes:
I brought it in and had the PSO replaced,...and it seems that PSO might not have been the cause.  i hope spark plugs will do it!  thanks!  mike 94 S4

Mike,
Unfortunately, it seems that some coil faiure modes will cause failure of the PSO. 
So check both before you replace a PSO. It appears that you could blow another one (PSO) if your coil primary is shorted. There apparently is nothing (fuse) to limit the current that the PSO sees if the coil is shorted, POOF $emiconductor $moke. 
Please correct me if I am wrong anyone, but my PSO failed simultaneously with the coil, which tested shorted upon removal.

John

John Tilden
1995.5 S6 Avant Europa Blue
Bellevue WA
j.tilden at verizon.net