[john walker's workshop]

....to the lambda relay, which powers the computer, which works the frequency valve, which makes the engine run right. the relay is the usual culprit. warm the engine and at idle, unplug the relay and see if the idle gets funky, or no change. it has to get funky, unless it's there already. like konish says, check the fuse first. the relay is under the front of the passenger seat, toward the tunnel.