Strange A/f behavior while pig rich. I have an drunken hypothesis.

Bluedemon_II

New member
Is it possible that an engine could run so rich that combustion would be erratic and a wideband would read this as a lean condition due to most of the fuel exciting threw the exhaust?

My wideband "LM-2" Read 19.2 at idle on a engine that had plug problems and was missing like crazy. I adjusted the fuel thinking it was lean and didn't notice a difference. I checked the plugs and found that they where totally fouled. Change them to brand new ones and the problem persisted. Dumbfounded I decided to change the map and put the original tune that I had made and the problem when away. I reflash the rich map and it started with the same behavior.

So Using internet and medalla logix I guess that if there is to much fuel for combustion to take place, the wideband will read lean?
 

HolyCrapItsFast

Drinks beer!
That is possible because the O2 sensor is meant to measure the oxygen in the combusted exhaust and if there is all unburned fuel in the exhaust stream then little combustion took place so oxygen content will be high.

You should also check your fuel trims against the wide band and see if they are going in opposite directions. That will indicate a bad O2 sensor and switching maps may just be the difference between running open loop or not. It depends on the map but after a reflash you could be in open loop for some time before if reverts to correction mode. The way to check this is to flash the ECU with your "rich" map and unplug the O2 sensor and see if it runs properly when you force open loop. If not then I suspect maf scaling or latency and it is back to the drawing board for you! :lol:
 
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