I would like to bypass the defective oxygen sensor in my 1989 Ford
If I jump the signal wire out and signal return terminals on the
computer, will the computer think the phantom oxygen sensor is reading
"rich" or will it determine that the voltage reading is out of spec
and then go into a constant medium richness mode?
I am going for maximum fuel economy. I drove the truck like this for
about 100 miles and it ran fine, except the check enging light would
go on after the engine was driven for about 15 miles at highway
Thanks in advance.
No... the PCM will refer to the default "look-up" tables.... this will give
"safe" fuel and timing curves.... meaning a more fuel than it really needs
and less timing than it can use. For maximum fuel economy, the "feedback"
system needs to be up to snuff and working properly.... this will allow the
PCM to offer the best fuel economy with the lowest emissions....
Much like the computers we use to communicate, the PCM in your truck process
what information it is given.... If the info isn't accurate, the
computations wont be accurate.... We used to call it GIGO (garbage in garbage out).
'Maximum fuel economy' without an oxygen sensor? On a fuel injected engine?
How about minimum fuel economy and an engine that barely runs at all and
doesn't live too long? Perhaps 'Tom et al' will tell you something
different, but in my humble opinion running a fuel injected engine without
an oxygen sensor makes no sense at all. A shorted sensor input (which will
be interpreted as constantly lean) will make the computer run the engine in
an 'open-loop, limp-home' mode. The check engine light will be the least of
your problems. You will have horrible economy, poor performance, a catalytic
converter overloaded with unburned fuel, engine oil diluted with gasoline,
So the question is why in the world would you not replace that defective
sensor. They cost about $50.
And incidentally, are you sure that the oxygen sensor is defective at all?
With all due respect, many people read a 'lean' or 'rich' code from the
computer and assume that it's a bad sensor. It's akin to putting a
thermometer in your mouth, finding 102 degrees, and instead of going to the
doctor, throwing the thermometer away.
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