...and yet another novel... > I can't find any vac leaks (which doesn't mean there aren't any). Try connecting a hand vacuum pump to various places and making sure that it holds vacuum. I recently found two leaks this way. One was my vacuum solenoid(!) and the other was the thermo vacuum switch under the intake manifold. It was leaking where the plastic meets the metal base. It is nice to do a vacuum test twice: Once with the engine stone cold and then again after it has warmed up. This way you can see if the vacuum signal switches from the warm-up regulator to the distributor advance. All of these connections should hold vacuum. > The idle was a tad rougher, only noticeable by ear. The tach never wavered. Not all tachometers are alike in these cars. Mine, for example, has a very slow response time. I can hear the engine seeking, but the tach needle doesn't move. I've seen other DeLoreans with tachs that bounce all over the place. Volt meters have variations too. Mine has a fast response, so it fluctuates with RPMs at idle while the tach sits there like a rock. Other DeLoreans have volt meters that are as slow as molasses. > Mine goes to 30, climbs to 45 and just -drops- back to 30. The range is close, but isn't it supposed to be a steady rocking back and forth vs. a climb/drop sort of motion? Yes. If your readings fluctuate very far then it could be that your mixture is far enough out of adjustment that the lambda ECU is intermittently switching to its default 50% duty cycle value. First be sure that you are reading your dwell meter correctly. Maybe you are confusing degrees dwell with percentage duty cycle. Also the dwell meter I have (Actron CP7605 available at Sears, NAPA, and various other places $40 or less) doesn't have any degree scales that match what I think it should. I just consider a full scale reading to be 100% duty cycle or 90 degrees dwell; and likewise, a half scale reading is 50% duty cycle or 45 degrees dwell. The half-way mark is the only one that you really need to measure accurately for adjusting the mixture screw. I think your neighbor Mike Cohee has the book Bosch Fuel Injection & Engine Management by Charles Probst. And in Chapter 6 page 32 it better explains this procedure. As a reference, the dwell meter should show 45 degrees or 50% duty cycle when the O2 sensor is disconnected (open circuit) or out of range. This should help you find the point on the scale where you should use to adjust your mixture screw. There are several possible snags along the way that can prevent you from getting a proper reading. The biggest snag is trying to make this adjustment on a car that is not running correctly for other reasons such as vacuum leaks or uneven flow rates through the injectors. If one injector is coming on late or not spraying like the others then you will end up with an adjustment that has one cylinder too lean and the rest too rich. You may get a reasonable average reading on the dwell meter, but the engine will still run like crap. Check the plugs to see what they tell you and also check the flow rates of all the injectors. If the O2 sensor is giving a signal that is too far out of range (such as running too rich, too lean or having the sensor clogged with soot) then the lambda ECU will default to 50% duty cycle. This can really fool you if you don't know what to look for. You want to adjust it for 50%, and you see it at 50%, but it is at 50% for the wrong reason. If you get the adjustment half-way close then the sensor will intermittently give a value that the lambda ECU will try to work with. When this happens your reading will fluctuate by a large amount as the O2 sensor goes in and out of range. When I start one of these adjustments from scratch (such as after replacing the fuel distributor) I adjust the mixture to be too lean while the car warms up. If it is too rich for too long then the O2 sensor may get sooty and stay out of range. It's lots of fun standing behind the car smelling exhaust fumes until you are ready to pass out. It's best do to this out in the open on a windy day. Walt Tampa, FL Yahoo! Groups Sponsor ADVERTISEMENT <http://rd.yahoo.com/M=244522.3707890.4968055.1261774/D=egroupweb/S=170512 6215:HM/A=1595055/R=0/SIG=124j83ehr/*http://ashnin.com/clk/muryutaitakenat togyo?YH=3707890&yhad=1595055> Click Here! <http://us.adserver.yahoo.com/l?M=244522.3707890.4968055.1261774/D=egroupm ail/S=:HM/A=1595055/rand=722679837> 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/> .
<<attachment: winmail.dat>>
Back to the Home of PROJECT VIXEN