my z has 133,000 miles on it . my waterpump is leaking . so , i decided to do a complete tuneup including opti . does an opti really cause all that much trouble . i am not buying an expensive one . my car is just an everyday driver . also , my mass airflow sensor is bad . what exactly does it do . all i saw is a screen in it . i had my cats checked and they are good . but , my ses light says o2 left bank . where can i get 02 sims cheap . i live in texas . the exhaust place says that should cure my problem . any and all help is appreciated . thanks jay

 

Maf's read how much air is entering the engine to make the air/fuel ratio. The bad o'2 will cause all kinds of running problems. I would fix that first and then go from there. How do you know the maf is bad?

 

The Opti is the distributor.... if it fails, you have erratic spark or no spark. Did you have a problem that led you to the conclusion you needed a new one? Many have lasted over 100K miles. If the leaky water pump didn't ruin it, it might not have needed to be replaced.

Not sure what "not buying an expensive one" means, but you are best off getting the genuine GM full replacement, and buying it from one of the discount dealers that are mentioned here often.

http://shbox.com/1/4th_gen_tech2.html#Dal_and_Jason

As noted above, the mass air sensor measures exactly how much air is entering the engine. The PCM uses that number to determine how much fuel to add, controlling the A/F ratio. There's nothing in there but a "hot wire" that measures how much heat is lost to the incoming air, and a thermistor to measure the temperature of the incoming air. Without the MAF sensor, the PCM will default to "speed-density" A/F ratio control. As long as your engine has not been "altered", speed-density will work fine.

As far as the O2 sensors.... What is the EXACT code you have for the left bank O2 sensor, and EXACTLY which left bank sensor is it (there is one before the cat and one after the cat)? Often, O2 sensor codes are caused by problems other than the sensors themselves, and you might just be wasting your time and money replacing the sensor if that's not what's causing the problem. If its the pre-cat sensor, you can't replace it with an O2 sim, only the after cat sensor.