Figured I'd start a new thread since I'm delving into CIS-E troubleshooting here. Basically my car failed emissions pretty grandiosely. HC 3.4 (Limit-1.5), CO 120 (Limit-20). I replaced the O2 sensor and my semi-stuttering idle, and cold/hot starts got a lot smoother. I took it back and failed even worse than before. I know there is something broken in the fuel control system.

I will mention that there are no driveability issues at this time. It's got power everywhere and idles smooth. There are no driving "symptoms" other than being a gross polluter. This is not a Cali car.

I don't have access to a meter than can do Freq readings ATM, so I just used voltage. With the engine off (ignition on) between pins 2-3 of X11 there is a 12.2V reading. I noted that deflecting the air flow plate DOES NOT change this number at all. Both WOT and partial deflection of the plate have no change on the duty cycle reading.

With the engine running (warmed, idle) the voltage between pins 2-3 of X11 is 9.4V and is fixed. The 9.4V will jump to 7V (50% duty cycle) only when the engine is revved semi-hard. If you raise the throttle to a steady, high RPM it still stays at 9.4V.

What's the next test?

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1991 300E - 212K and rising fast...