Quote:
Originally Posted by NOLAsc
Back to the problem at hand … no box under seat means no Lambda, right? That blowing interior light fuse still bothers me a bit since on US cars, that fuse powers the Lamda stuff.
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If an engine has no cat, it will not have an O2 sensor, thus it also won't have the control unit for an O2 sensor.
The blown fuse has nothing to do with it.
Like I said early on, it sounds like a lean misfire. As Bob pointed out, that can be caused by a dirty injector that has less output than the rest. When you measure the CO (assuming that is done correctly) you are measuring the average of all 6 cylinders. You can have a CO number that is withing range but still have a problem, if not all 6 cylinders are firing equally.
When he reported that the AFR was a certain amount, that was a red flag because Porsche never specified the AFR as a tuning measurement. You can convert that to a CO %, and that AFR isn't far off the range of CO that is correct for that engine, but why not report the CO, if that's what we are supposed to use for tuning?
My advice was to have the CO measured, using the correct machine and procedure. The tech books tell what the ideal number is for each CIS engine and gives any specific instructions for testing (like disconnecting the hose from the air pump first, etc.) for each particular engine type. You might test different engine versions in slightly different ways.
Assuming the fuel pressures are correct, as he alluded to earlier on, it would be a good idea to check the injector flows. It's somewhat a given to make sure the ignition system is in good order, before doing all of this. I would certainly inspect the distributor, as many people don't do any maintenance to the distributor on cars that don't have points, like an SC.
JR