Quote:
Originally Posted by benzborg
Key in the on position reads proper spec - 12.4 I believe? When I start the car we got a reading of 2 volts at idle. A mechanic close to home has done this test a couple of times. The spec I believe he said was around ten? I know that's a very rich reading. He has a similar 300E giving approximately
the same low reading but in spite of this his and my car run pretty well. Fuel economy suffers but oh well.
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UH OH.
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If you are getting 12.4V with the key to on, that means the lambda system is not operating at all, it's not making any adjustments to the mixture. Your car is not going into closed loop for sure!
Ok. So referencing the factory manuals. 100% duty cycle with the key on, means that the system is "Operating without fault recognition". Which is not good.
Quote:
Without Lambda Control (100% reading)
1. No voltage or ground at KE control unit (N3) or KE control unit (N3) faulty
2.Overvoltage protection fuse or overvoltage protection (K1/1) faulty
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KE control unit = ECU. And you've already put in a new OVP. Can you swap a good used ECU into the car? I believe that might be your culprit. I just replaced the ECU in my car, because I had failed emissions by 4500%! They
do go bad. Which is what your lambda reading is indicating with the key on. My bets on that! Once you replace the ECU, that 12.4V should turn into exactly 7V. Then you will be able to take a real reading at idle, and the adjustments will actually be doing something. You want the voltage at idle to swing about 1V on either side of 6.5V.