I have had a problem with my engine for a while (454 controlled by 1227747 with Holley TBI), which I kept thinking was just a lean condition. I kept running my BPW up and up until it seemed to run better, but I still kept getting an engine miss.

I finally watched with the lights out in a dark garage and found that one cylinder wasn't getting any spark at all, at least sometimes, because the wire had pulled out of the boot and was arcing directly to the block. This cylinder is on the same side as the O2 sensor.

So, my question is, what does a non-firing cylinder do to the O2 reading? Does it make it appear artificially rich or lean or neither? Anyone know?

Thanks,

John.

 

A none firing cylinder (as in the case you mentioned) means a huge slug of O2 passing the sensor. O2 would see that as lean.

 

Makes sense. So, the engine would try to compensate by richening things up when in closed loop mode. But, it would also try to compensate some in open loop mode (PE, idle), right? I'm just trying to make sense of the before fix and after fix engine operation.

It seemed to be running a little better, except for the miss, but now with no miss, I think it runs a little leaner than it should at Idle (454 bins run open loop idle by default).

 

Yes, the (already learned) BLM values are still in use during open loop.

RBob.