Two quick questions about o2 sensors:

1) Are they affected by changes in other engine parameters? For example, if your tuned perfectly, with 128 BLM's all the time, and then change your timing, will the o2 sensor readings change?

2) How close is too close to an exhaust port? I added an o2 sensor to an older car. It's about 4" from the nearest port. Can't put it down further unless I put it in the pipe, not the manifold.

Thanks

 

1) sometimes.

2) You want to read an average. Looking at one cylinder if it has a problem such as a vac lean at some time, might mean about walking, because of it reading sooo low. Some cars don't run well on the defaults. Pipe is fine, and if too far away using a heated one will cure the problem of too cool of exhaust.