86 4rnr timing jumper terminal issue

[Throttle Slave]

I am having a problem with my timing jumper plug, sometimes when I jump (short) the connectors on the left fender the idle drops and the timing light will read the true timing. However jumping the connector doesn't always work, sometimes it makes no change in idle or timing at all. My wire diagram doesn't show that (2) wire connector or what it connects to. Could anyone give me an idea of where to look to resolve this issue, thanks for any help...