1979-1993 & 94 Conv [Subscribe to Daily Digest] |
So I eventually fiddled and finagled my way into the O2 sensor's black wire "test plug" behind the PS reservoir, but only by breaking off half of the plastic spade mount :( Love how all this brittle, crusty-yet-critical crap WON'T detach as designed until you've all but destroyed it...
Anyway, as installed the 'new' AMM showed 480 Ohms between pins 3 and 6, and voltage between O2 wire and ground oscillated between .1xxx and .85xxx, sorta settling briefly and more-or-less evenly at either extreme before swinging away. I'm using a DMM whose display is kinda crude for this, but that's only because I've yet to read the 1/2"-thick manual and discover its plethora of fantabulamultiplexular adjustments and functions; hopefully I'll find one that zooms into the 0-1V range and gets a little closer to real time reactivity, maybe graphing it as well...
So out of curiosity I tested the prior AMM, during whose tenure the motor never got so hot so quickly and found ~600 Ohms between 3 and 6. Went back to the new one and eventually added about half a dozen clockwise turns on that brass adjusting screw while idling: Never really noticed an obvious difference in O2 signal voltage behavior, unless maybe it went just a *little* lower and higher and settled at each extreme slightly longer?
Not sure how to interpret that reading, since I can't find it *quantified* anywhere just what I'm aiming for. That adjustment was largely arbitrary.
DRIVING it, however, showed an immediate and unmistakeable difference: More <lunge> for any rpm and level of boost, more moderate warm-up curve, and an extended 80mph cruising temp _without_ the heater cranked that is lower than it was previously With the heater helping out... back to normal. Now AMM pins 3-6 show just over 700 Ohms.
So until I see curds in the oil, bubbles or oily sheen in the coolant, and/or cooling system overpressure I'm neither buying the leaky headgasket theory nor the $45 kit to test for it (edible words, I know).
Obviously it was running lean and consequently hot, obviously I should devote some time to checking for vacuum leaks, obviously I should work my way through every basic fuel check and adjustment Bentley offers, and I'm going to change out coolant/Tstat/radiator just for... y'know, Summer, since it's been quite a few. But I'm still wondering how to know when I've pushed it too rich: Will the motor start to stumble or something or plugs quietly accumulate deposits or will my gas mileage suddenly just suck? This next tank will be telling... I'm just wondering now what's at risk running a possibly rich mix here?
posted by 98.90.76...
, Sat, 16 Apr 2011 15:50:04
, Sat, 16 Apr 2011 19:06:36, Sat, 16 Apr 2011 15:57:59
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