Green plug on 85 Regal 3.8

[Steve ~REGALIZE IT!~]

I'm a Junior in high school and my autoshop has an 85 Regal Limited with the 3.8 V6 (non turbo). It'd most definetly the bitchinest car in the shop. when everyone else is working on thier ricer Honda's , were working on the Regal

Anyway, theres a wire with a green plug on the end. Its located in front of the carburator, kind of coming in from the left side(Left if i'm looking directly at the front of the car)
For the life of us we cannot figure out where it goes. Can someone help me out?

Thanks , -steve

 

[GP403]

A/C Idle compensator? What's the plug look like? [EDIT: duh. idle comp wouldn't be on the left would it! ]

 

[85_SS]

It is a diagnostic connector for connecting a dwell meter to monitor the mixture - it is not supposed to be connected to anything (although GM should have at least had a cap or plug for it to keep it clean).

 

[joe_padavano]

To expand a little on the previous reply, your Regal has an electronic feedback carb. There's an electric solenoid that holds the two tapered metering rods for the primary jets. As these tapered rods move up and down in the jets, the resulting jet area gets larger or smaller (since the rods are tapered), allowing a richer or leaner mixture to go into the motor. The computer reads the O2 sensor, coolant temp, air temp, air pressure, etc, etc and pulses the solenoid up and down many times a second. The longer the solenoid stays down, the more the fat part of the metering rod is in the jet and the leaner the mixture. Conversely, the less time the solenoid is down, the more the thin part of the rod is in the jet and the richer the mixture. If you take the air cleaner off with the engine running, you should hear a buzzing noise coming from the carb. That's this solenoid being pulsed up and down.

You can read the duty cycle of the solenoid by connecting a normal dwell meter to the green connector. Set the dwell meter on the 6 cyl setting (that's unrelated to the number of cylinders on the motor, it's just how this system works). With the engine running and warmed up, the "dwell" reading on the meter should be somewhere between 5 degrees and 50 degrees. Ideally it should be around 30 degrees at idle. If everything else is working properly, you can adjust the idle mixture screws to achieve 30 deg with the engine running. This is how idle mixture is adjusted on these cars.