Hessitation in Late Model Subarus

[G. Scott Ponton]

I have been following this thread for a while. There are other refferences
to knock sensors and problems with "sensing" other engine noises in the
arcives too. I have been running a old Pontiac with a custom distributor and
ESC for several years (9). The engine has a solid grind cam and several
other sources of "external" knocking. The only time I have ever had problems
with the sensor picking up stray noises was went the oil pump drive broke.
Although the rods weren't knocking audibly the ESC was retarding the timing.
    I think Gary is right with his assumtion that the Subaru computer is
"too sensitve". As I have never checked I am not sure but I would guess that
the GM ESC/EST has a built in filter to eliminate certain freqs and
amplitudes below a point.
    When I first installed the system on this engine I was worried about the
ESC retarding the timing because of the solid cam too. So I spent several
hours with a 'scope checking the output from the sensor and checking to be
sure the timing wasn't being retarded. The system worked/works perfectly.
Now I can drive my old 11:1 pontiac anywhere on pump gas. Then if I want to
race it I just fill it up with racing fuel and away I go.

Scott