mixture adjustment woes

[Alan Pritchard]

ok guys, tried twice now to no avail....
culprit is 1990 90q
initially (because i didnt have the harness) i set the mixture by
disconnecting the o2 sensor and measuring its output. this worked ok.
so i have made a harness as described. 1 wire goes from cpa to multmeter,
other connection on meter goes to the loom (same pin), another wire jumpers
between the other pin on the connector, and the other pin on the cpa.
car is run up to temperature and the meter (tried several) jumps between
120ma and 80ma at idle, occasionaly drops to 30 ma and up to 140ma. so, wind
the mixture screw in a tad..... and virtually no effect. a quarter turn
drops the reading to about 105-80 ma (rough averaging), but idle starts to
get really lumpy, also revving the engine shows the engine to be sluggish.
so where am i going wrong??????
ive got new plugs, dizzy cap and rotor arm to go in tonight, so ill try
again later maybe!!!
any btdt please.
thanks.