Quote:
Originally Posted by stlrj
The brown wire on my 87 was never disconnected when I failed but the CO adjustment did the trick in my case.
Keep your fingers crossed, you may be lucky.
Cheers,
Joe
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Something does not sound right there. Sal maybe should comment further on this. He already mentioned that the DME is programmed to maintain Lambda. If you watch the exhaust gasses on a wideband gauge, you can see that it certainly does. If you open the oil cap, the mixture will spike to lean and then quickly adjust fuel pulses to return to Lambda +/- .2. Similarly, if you unplug the vacuum line going to the fuel pressure regulator, then it'll spike to a rich mixture, then quickly return. If you open the CO mixture screw all the way until it falls out, the DME, once the O2 sensor has warmed up, will return the mixture to Lambda.
What this means is that there really is no adjustment of CO% per se. What you are doing, when you disconnect the O2 sensor and adjust CO%, is to return the mixture to baseline before plugging in the O2 sensor. IIRC, Motronic or L-Jetronic "likes" a slightly rich mixture to work from, like say 1.2 Lambda or even 1.4 according to some. If there is a huge vacuum leak letting in false air, then the system can be defeated and caused cycle up and down, constantly adjusting the mixture. Maybe baseline re-setting can make that cycle smoother, but I don't think at idle it would make much difference.