Originally Posted by
DMCVegas
That is technically correct...to a point. Which is why disconnecting the O2 sensor to force the LAMBDA system into open loop is the 3rd step you are supposed to perform before adjusting the AFR by way of the CO screw as per the Workshop Manual.
That way when you set the AFR it will be dead-center within the LAMBDA feedback loop spectrum of lean/rich. Once complete you plug the oxygen sensor back in to allow LAMBDA to reactivate & perform the fine-tuning adjustments as needed on the fly while driving. Otherwise the system is fighting you to where you tune it with a bias to one side. That affects on-the-fly adjustments where your engine runs terribly with too rich or too lean conditions during it's warm-up cycles, massive elevation changes, or WOT conditions.
This is why I prefer the Workshop Manual's instructions versus just always going by dwell alone. It demands establishing baselines across the board on component functionality & combustion chamber conditions to eliminate as many variables as possible, if not all. The duty cycle of the LAMBDA unit can vary during operation to achieve optimal emissions. So if you're going by dwell alone, you can end up fighting the engine which is counterproductive. Dwell is important to tell you that the engine is running properly, but you have to keep in mind that K-Jetronic is also a modular system. It was meant as a replacement for carbs, and still relied upon kicker solenoids and screws to set idle speeds until CIS was introduced. Then it had LAMBDA as an emission control device to fine-tune tailpipe emissions by independently manipulating the AFR on it's own. That's why you set the baselines, and THEN let the add-on devices (WUR, LAMBDA, etc.) control things as they see fit, instead of basing measurements off of their tampering. That's why the Workshop Manual says to set the 950± RPM with a 2000 RPM test and cleaning of probes, a set coolant temperature, and to insure Duty Cycle is @ 50% when disconnected before CO/AFR adjustments, And then no more than a 5% deviation from mean between 45%-55% with the LAMBDA's operation thereafter to ensure sure proper functionality. But it's all about achieving those baselines first.
K-Jetronic is great because when you install the correct, functioning parts, it only requires a single screw to turn for tuning. Yes, you need a couple of tools, but most you should already have, and it's still just a single screw. The trade-off however is that it does not suffer tampering nor accept compromise when tuning. Precision isn't hard, but it's also something that most mechanics with a "good enough" attitude can have a difficult time coming to terms with.