> Hm, also now that I think about it, a stuck WOT microswitch will also > override the lambda computer and freeze the duty cycle. Well what do you know Rich? One of the switches on mine was stuck, but it was the one for the transmission. (This is an automatic.) > If you pull the adjustment screw bung out quickly, does it stall? No. > If is > idles smoothly when warm but stalls when you pull the plunger out, it's > within 1/4 of a turn of the right setting. If it doesn't at least > struggle when the plug is pulled, it's either too rich, or you have a > vacuum leak. Martin, mine doesn't struggle at all unless I'm at the threshold of stalling from being too lean. I don't think I'm running too rich now, but the cat still glows. I replaced the oxygen sensor. For those of you into cross-references, this is a Bosch part I bought from Pep Boys for $29.99 Actually they have two that will do. The one that is the exact replacement costs much more. It is Bosch part #11037. The one I got is part #11027, and the compromise for the cheaper price is that you have to reuse the wire from your old sensor. But Bosch supplies a crimp connector on the end and a piece of heat shrink tubing ready to go. I tried telling the parts counter guy the old Bosch number, and he couldn't use it. For those of you into diagnostics, here is some info on the O2 sensor: It doesn't give a correct reading until it is hot. It works like a weak battery producing a voltage depending on the amount of oxygen present. This is a high-impedance output, so if you measure it then your meter must have a high impedance or it will drag the voltage down to nothing. With the sensor's output hooked directly to and only to a volt meter (no impedance load from the lambda ECU) and the car is running at the optimum air/fuel mixture (Lambda running at 50% duty cycle because sensor is out-of-range) then the voltage from the sensor will be 0.77 volts. Adjusting the air/fuel mixture screw either way will give a range from 0.3 to 1.2 volts. Anything outside of this range and the air/fuel mixture will be so far off that the engine won't run. So now that you have some background, here is what happened with my car today: I removed the original sensor and found it to be sooty black which indicates the car was running too rich. It's a real pain to change these sensors. I could fit the wrench on it, but then I wouldn't have room to turn it. I ended up using a variety of what ever I could make fit depending on the room I had for the handle as I turned it. This included line & regular crow-foot wrenches, and an open end/box end wrench. The sensor takes a 7/8" wrench. Is this close for a metric size? It would seem that anything from Bosch would be metric. So I hook up my dwell meter, start the car and wait for it to warm up. To insure that I'm not running too rich to make the cat glow again, I adjusted the air/fuel mixture (CCW) to the leanest possible setting where the engine would still run without knocking. By the time the car warmed up, the cat was glowing anyway. I let it cool off and try again later. This time I disconnect the O2 sensor from the Lambda ECU and hook it to a volt meter. I adjust the air/fuel mixture to get a voltage fluctuating around 0.6 to 0.8 volts. I fiddle with it a while noticing that the car is not responding to my adjustments like it has on other DeLoreans that I've dorked with. And in a few minutes the cat is glowing red again. This happened while the O2 sensor was hovering around 0.7 volts and the duty cycle was 50%. Based on all this, I'm starting to wonder if my cat is clogged up and that is the reason for it glowing. This could have been going on for a while. Unless one of you has a better idea, the next thing I'm going to try is to remove the muffler and look in the cat with a mirror. If that is inconclusive then I'll take the thing off and look through it. Yes, I could have a vacuum leak, but that couldn't be what is causing the cat to glow. Could it? Walt Yahoo! Groups Sponsor ADVERTISEMENT <http://rd.yahoo.com/M=251812.3170658.4537139.1261774/D=egroupweb/S=170512 6215:HM/A=1693352/R=0/SIG=11tralmvc/*http://www.netflix.com/Default?mqso=6 0178293&partid=3170658> click here <http://us.adserver.yahoo.com/l?M=251812.3170658.4537139.1261774/D=egroupm ail/S=:HM/A=1693352/rand=149901430> To unsubscribe from this group, send an email to: DMCForum-unsubscribe@xxxxxxxxxxxxxxx Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .
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