The reading on the X11 pins 2 and 3 stays at 2.90V (VOM set to DC, scope showing a steady pulse that doesn't widen or narrows as I try to change the duty cycle) and steady no matter where I adjust the tower 3mm screw.
I have adjusted the air flow meter potentiometer
I have replace the O2 sensor (New unit)
I have replace the EHA (New unit)
Could it be a temp sensor?
I am going back to the garage to check how the O2 sensor is reacting on its own. In the mean time, tell me what you think.
Okay, here is my update.
I unplugged the CIS temp sensor and the reading between pins 2 and 3 jumped to a steady 9.8V. The pulse wave widened on scope accordingly. This tell me that without the temp sensor in circuit the CIS goes to the other extreme.
Basically one extreme resembles the wave with the ignition on and engine off even if the engine is warm, that is the DC reading is 2.9V. The other extreme is when the temp sensor is out which brings the reading to 9.8V. The happy medium should be something in between with fluctuations due to the O2 sensor.
Having observed that I measured the resistance of the temp sensor while the car was warm. I got about 800 to 900 Ohms between the poles and 400 Ohms via ground.
Reading the CIS troubleshooting guide, I should have between 290 and 370 Kilo Ohms to ground.
I am reading conflicting stuff on the net and in the CIS manual itself. In some places it says at 80C the resistance should be between 290 and 370 Kilo Ohms and in others the range value is ONE THOUSAND times less, like 290 and 370 Ohms.
Which one is correct?
Location: Reading, Pa; Chester Springs, Pa; Larchmont, NY; Detroit Area (temporary)
This is all great information! My one question (for anyone): How does the CIS computer know that the temp sensor is shot when it is based on ohms?
The CIS computer takes information from the many little sensors within our systems, works its magic, then sends the correct signals to wherever, right? So, if the engine is running on the "limp-home-mode," then one of those incoming signals is way off. It sounds like your temperature sensor isn't too far off....but would that slight deviation from what the CIS computer expects force it into "limp-home-mode?"
I personally think you have a bad electrical connection somewhere. Maybe a bad fuse or relay somewhere? In my experience, 95-98% of the issues on my '92 2.3 have been due to:
1. Electrical connections (sand the connections to fix it)
2. or those damn ceramic/plastic fuses...and their connections in the fuse box.
1992 190E 2.3 8v (converted to 5-speed)
27,045 miles as of 9/31/08
135,000 miles as of 5/14/13
1965 Shelby Cobra 427S/C (351W engine)
14k miles as of 11/11/12
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