jon@dakota-truck.net wrote:
> William,
>
> This isn't a flame, so I sincerely hope you don't take it as such,
> I'm just looking for some clarification... :-) Based on your post, it
> sounds like after you used the resistor to alter the downstream O2 sensor
> signal, you got a check engine light? The main reason most folks are
> looking to simulate the downstream signal is to eliminate the check engine
> light, rather than to change engine operation, thus most folks would
> probably suggest that this method doesn't work. As far as the improved
> operation goes, I've seen many cases of the "placebo effect" when doing
> mods, is there any chance this could be what is happening?
This is a good question. I am very aware of the placebo effect, and try to
take this into account. The improvement is only when the engine is cold;
before I put this resistor in, the engine would even stumble occasionally in
first or second gear, sometimes missing in second for several seconds.
Dramatic power loss. These things never happened before I removed the cat.
>
>
> Just to interject a theory here...
>
> Based on what I have read, the downstream O2 sensor isn't *supposed* to
> have an effect on engine operation, its basically there to tell the
> driver when its time to buy a new cat. However, I have seen posts from
> people who are convinced it actually does have an effect on engine
> operation, so perhaps it does.
Same here. the Haynes manual I have sez the same thing, but people here
disagree. Hmmm.
>
>
> Anyway, on to the theory. In order for this to make sense, we have to
> assume two things:
>
> 1- That the downstream O2 sensor has an effect on engine operation
> 2- Since you were getting no check engine light before, the computer was
> operating under the assumption that your cat and downstream O2 sensor
> were operational. (Otherwise, it would have turned on the check
> engine light.)
>
> My theory would be that the computer was adjusting the operation of the
> engine based on bad data from the downstream O2 sensor, causing the
> engine difficulties. When you inserted the resistor, the computer
> either detected that the sensor was bad or the data from the sensor was
> far enough out of whack to cause the computer to assume either the
> sensor or the cat is bad. In either case, the computer would now ignore
> the data coming from the downstream O2 sensor, and cease to (mis)adjust
> the engine based upon that data. If that's the case, I suspect the
> same engine improvements could be had by simply disconnecting the sensor.
This is another good point. I'll try it and post the results. One minor point
I forgot to mention is that I unhooked the battery and let the computer reset
itself when I installed the resistor. Don't know if this might be relevant...
>
>
>
> --
>
> -Jon-
>
William
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:03:22 EDT