EA problem- oxygen sensor?
ok there is an annoying problem with a friends car. when you hold the car at a steady rpm, say 2000 rpm the engine is a bit rough, the tacho needle moves around a tiny bit and you can hear tiny pop...pop pop... ect from the exhust. It is noticable when driving, described a bit like the car is pulling back, a lean mix i guess? now the thing is it doesnt do this, and in fact runs perfectly when you disconnect the oxygen sensor. I tried another oxy sensor in it today but no luck. There is a couple tests described in the gregory's manual which i tried today, it was for .85 volts at the black wire, and it should flick between .1 and .85 volts after 40 seconds or so. I got around .73 volts though with that test. could that be enough to cause such problems and where should i start looking to find the cause of it ?
its done this since converting it to mult point. vacuum leaks have been checked for. im confident there is no proplem in that regard.