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Old 05-12-2003, 07:49 AM
stevebfl stevebfl is offline
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
I hope you figure this all out.

I have been working on this system for years and nowhere was anyone dealing with this. I mentioned that we were told of the adjustment pot but I doubt that we were told what voltage to set it to. I have learned more in the last 6 months about this than maybe the other 19 years since the KE system came out with the 190.

So, I probably can't be much help here except to remind that the voltage is due to the position of the airflap. As the idle valve changes airflow the plate moves. I attribute the difference between the cold and warm values to this difference in airflow.

An idle of 1000 rpms is too high, so you have a problem. From these discussions we have figured that the idle strategy of closed loop rpm control does not start till the AFP (air flow pot) voltage gets below some value probably .75v. Did it happen? This is where diagnostics and learning have a lot in common. How would we know; no scanner to tell us the control unit recognized closed throttle position (CTP)?

What does control look like? Control is done by pulsing current through the valve. Different current different airflow as the valve moves. This is best viewed with a scope while calculating duty-cycle. So at idle the current if measured with the same harness as EHA should be about 600ma. Turn on the A/C you get another 50ma from where ever you are in control. If you have an airleak and the valve is commanded totally the current could probably reach an amp; I have seen .9a+.

What you will see on the scope or duty cycle is the relative amount of ON time. The maximum duty cycle used is about 70%. So if you find the valve in 70% control it likely is doing all it can to shut down incoming air. If in doubt shut down air until the control duty cycle moves. Think about that one for a while and think about getting the airflow down before you worry too much about adjusting the AFP.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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