Re: Confused new lister

["Paul Robertson" <robepa@wwc.edu>]

Dear Confused Lister,
The O2 sensor is mounted in the exhaust line just ahead of the cat. The O2 sensor(called the "lamda sensor" by Bosch" reads the oxygen content in the exhaust. From this it can tell if the air fuel mixture entering the cylinder is rich or lean. Rich means too much fuel for the air, lean means too little fuel for air. The mix that the injection system is trying to deliver depends on conditions but is usually close to 14.7:1. That is in mass of air:fuel. The input from the lamda sensor is VITAL for the motor to run well. As far as if you need a new one... Impossible to tell with the given info. the manual gives specific testing procedures that will answer that. I would bet that if it is the original sensor it is past it recommended service interval. That does not mean that it is bad my 86 4KQ has the original O2 sensor and it still works great. I have verified this by the manual specs. But i don't think that it is the cause of your idle problems. this is usually caused by a leak in a vacuum
line. I am not too familial with your ride so...
Air-mass sensor
the air mass sensor is what tell you computer how much air is entering the engine. The computer delivers fuel based on how much air is entering the engine. The sensor heats a platinum wire ti 175 deg above the air temp. The air flowing by cools the wire and the computer has to increase the voltage to the wire to keep it 175 above air temp. The computer uses this voltage to actually read the incoming air flow. If it is bad it will cause all types of problems, rough idle, poor starting, ect.
your car does not have an altitude sensor. This is because you air sensor measure MASS of the incoming air regardless of temp, altitude, ect. My car's air flow meter measures volume nt mass. It NEEDS a temp and altitude sensor to calculate the mass of the air from the volume. If the mass air flow sensor is bad then the computer may be using a default curve built into it for sensor failures. Also you idle is controlled by the ISV (idle stabilizer valve) Check that.
Also check the fault codes, kind of complicated but very doable. All this info is in a great book (Bosch Fuel Injection & Engine Management by Charles O. Probst) It can be bought @ amazon.com for about 30$
Good luck!
Paul Robertson
robepa@wwc.edu