This is my first time doing this! The reason for doing this was that I have replaced the EHA, 3 vacuum actuators in the climate control that were leaking, the rubber boot on the Air meter and cleaned the carbon from the throttle valve. I bought a new Digital Volt Ohm meter from Sears that has the Duty cycle setting on it. On my 89 300 SE with the M103 engine I was trying to get a reading from it from the X11 port using pins 2 and 3. At first I got nothing! Tinkering with it and reading the board I found that I have to go to the port by the battery with the LED Press and hold for 4 seconds see that nothing is stored and then press and hold for 4 seconds. Now I am getting duty cycle readings. I thought that diagnostic port was only on california cars? Mine has been a Washington state car its whole life. Anyway, Key on Engine off shows 30% duty on my DVOM. HMM thought it should say 70% for a federal car? Is the duty cycle reading 100 subtract the DVOM reading? Now I am sitting here wondering if I had the leads to port 2 and 3 backwards since I had it in and out multiple times trying to get a reading and getting a little frustrated. So I start getting readings and its going well. Engine running idle in park shows 55% with bouncing the decimal around pretty regular. Its got a lumpy idle with a tick almost like a miss while in drive. I set it to 45% reading on my DVOM (4 - 5 volts) so possibly a 55% duty cycle and its much better today. No tick/miss and not lumping at 500 but at 550-600 and smoother. I must say this is an interesting car to work on I wanted a challenge and well I got it! Its been nice to see my work payoff with a smoother idle and NO stalling in over a week! I did the Fuel pump relay and the OVP for that one. Since setting the Duty cycle last night my Economy gauge is half way between the stop and the start of the red. It used to lay right on the start of the red. So things are getting better.
Seems I wrote a book here. Thanks for reading.