"The frequency valve is turning off right before it happens and comes right back.
It is not ridmic and it is random so.
Could i just assumed that the valve needes replacement or is it turning off because it is being told to?"

I would not suspect the frequency valve itself. I think my 1st choice (cheapest) would be the "Lambda Relay" clipped on the left fender rail near the headlight hi/lo relay.
That relay has 2 output terminals that may be near "end of life":

• 87 — gray wire to Lambda ecu 8
• 87b — green wire to F Valve (then brown wire from FV to ecu 15 for FV control)

Momentary voltage failure at either terminal (or the FV connector) could cause your FV symptom. First try taking the FV connector off and on a few times to clean its contacts—then see if the symptom goes away.

If you decide to replace the relay, it is Bosch #0332-015-001, with tab for mounting clip.
The Bosch 0332-015-006, 012, or 013 will also work.
These have no mounting tab, but can be tie-wrapped or similar.
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.