Latest post of the previous page:
Thank you for responding to my post....I hope to not offend anyone as I'm not a VW owner, but wish to learn from your knowledge base on a similar AFM system. Funny you ask, it actually happens to be a 1978 Datsun 280Z. Reason I joined is that I came across your AFM Adjustment write-up and it happened to be the only one on the web that explained everything which I was searching for...the Datsun world could benefit from your knowledge as we use the same Bosch system.Amskeptic wrote:
What vehicle are we dealing with?
As a side note, my AFM has the fuel pump cut off switch, but the harness/ecu does not utilize it....there are no pins in those 2 locations. Do I still attempt the suggestion for the wiper to best idle and lean it out?Amskeptic wrote:Reset all to original locations.
Turn mixture screw to 2 or 2 1/2 turns from the bottom.
With warm engine, adjust wiper to best obtainable idle. Now lean it about 25 to 50 rpm.
Check that the fuel pump shuts off when you kill the engine and turn on the ignition only. You can bend the shut off arm carefully, making sure that you do not accidentally move the wiper in its slot.
Perhaps I misinterpreted the results...I'll have to reference my notes, but I was testing the movement of the wiper/weight assembly CCW and CW after adjustment to the cog wheel and was attempting to achieve that slight change in RPM when fingering it CCW. When fingering it CW, it responded with the slight drop in rpm, instantly at one point (have to look again at notes). So I kept adjusting the cog wheel to keep that slight CW drop, but achieve the slight increase in RPM when going CCW to get it in the brink of lean.Amskeptic wrote:Your adjustment procedure inadvertently chased after a result that was just not forthcoming. The engine should have responded to your incremential adjustments long before you traveled around the whole cog.
Keep the cog on stand-by and get the wiper closer to optimum.
I'm going to re-verify my valve adjustment settings this afternoon prior to any AFM adjustments. Can you explain what you mean by "engine not breathing efficiently due to NO vac leaks"? I'm displaying healthy vac at idle with the AFM bypass screw set from full close up until about 4 turns out...then vac starts to dip below 17 In/Hg.Amskeptic wrote:Keep in mind that valve adjustments and ignition timing have great bearing on idle airflow. I sense that your engine is not breathing as efficiently as it should, taking into account that you declared no vacuum leaks. The end result does NOT require a "no change in rpm" when you nudge the wiper to check mixture. A little evidence of leanness is OK. How do you test your results? Do you have LM-1, CHT gauges, known performance benchmark? We also need to ask your spark plugs after a couple of hundred miles.
Most of my results unfortunately are having to go by reading the plugs after a country drive and listening/feeling what the motor is responding to. I have a non-catalyst exhaust and no bung for a wideband sensor unless I weld one in. I'm currently using a vacuum gauge, rpm/dwell tach meter, and my ear to get this motor in the ballpark. New spark plugs after a couple hundred easy driving miles of use started in the lean, I had some white deposits on them. Then I started to play with the AFM, which led me to you!