Duty cycle for 300E Idle Speed Control
 

Does anyone have the integrated duty cycle values for 86 300E @ Terminal 3? How about EHA Milliamp readings? Anyone who has messed around with it, sound off! I would appreciate it and the neighbors wouldn't have to hear my language.........

You are supposed to read 50% duty cycle with the engine warmed up and idling. Also you must push down on the allen as you turn, or it will not change.

I would suggest that you search for threads on "Lambda Adjustment".

Good luck,

Actually any specific reading 50%, 60%, 90%, 10% etc. indicates a specific fault code.

To be sure that you are in sync, try key on, engine off. The reading should be 70% if a federal version or 85% if its a CA version. Once your are in tune, the constant reading of any multiple of 10 is a specific fault code. A proper running engine in closed loop will not be steady but an oscillation of a few percent about some value. The value to which it centers about indicates the relative mixture. MB would have the final setting oscillate about 50%. A steady reading of 50% indicates an inactive O2 sensor (fault code). I usually set mine at 40-45% as this puts the system slightly rich for everything not at steady state (and cold running).

The EHA ma should be about 20ma KOEO (key on engine off). When in closed loop at MB setting (oscillating at 50%) the ma should also rise and fall about 0ma. Lambda control can move 10-12ma in either direction (- or +) for correction. On decel you will see -60ma fuel removal. A quick acceleration wil give 6-10ma of correction from where ever you started. On cold start the combination of cold enrichment and starting enrichment can be +50-60ma. The key when warm is to observe closed loop operation (cycling between rich and lean to achieve lambda).

There is more about this in the article in the DIY section called Evaluating engine controls.

Thanks for the input folks ALL of which helps, the big question is the duty cycle for the Idle speed stabilizer...........I know there are 3 pin and 2 pin versions, how is the duty cycle read? From pin to pin or a specific pin to ground? Also, Cold start, closed loop question....how can you tell if the preprogrammed parameters for idle/mixture are good? How about the quality of the speed signal from the distributor to the TD/Fuel pump relay are good? Thanks again!!!!

Duty cycle is not the normal way of looking at the idle circuit although looking at it with a scope can show whats happening from a qualitative view.

Because both sides of idle motor are hooked to the controller (unlike V8s which are powered on one side and grounded by the controller) current is the way its viewed. Normally the idle should be at proper speed with a current around 600ma. Adding A/C should add 50ma. Adding load, by turning the steering wheel say, should increase the current and the speed should stay the same.

As to the speed signal take a look at my other article about A/C. It shows scope patterns for the crank sensor and how it looks after the ignition changes it to a pulsed DC signal, which is used by the FP relay and the Klima relay, MAS or whatever.