electronic carbs

[Plunkett]

So my 86 chevy silverado has a 305 with a 4barrel quadrajet carb. I didn't know it till the other day but it's an electric carb. What exactly is the difference between that and a normal carb? It looks like one of the wires from the carb goes to a spot that is screwed into the intake manifold. Thanks in advance.

[Malo83]

The E4ME Qjet has an electronic mixture control solenoid mounted in the float bowl to control the air-fuel mixture set by the ECM, this would be the blue plug in the pic, the brown plug on the carb at the 5 o'clock position is the TPS (Throttle position Sensor) also monitored by the ECM.


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[Plunkett]

So can you physically adjust the air/fuel on the truck with it being an electronic carb?

[Plunkett]

I just went out to my truck and I don't have the throttle position sensor on my carb. I have the blue connection on the inside of the carb tho.

[Slonaker]

Unless it is a CA emissions truck, it is not an electronic carb. The '86 has an electrical connection, but it isn't controlled by a computer. I believe it is a solenoid, controlled by engine temperature, that is used for the accelerator pump.

I might have some of those details wrong, but it should be pretty close.

Yours should have a small harness that goes to a sensor on the thermostat housing and somewhere else.

Slonaker

[Plunkett]

Slonaker, that's exactly how my carb is. It has a spot on the thermostat housing, which that sensor is broken on the thermostat.

[Slonaker]

Mine was broken, too, when I got it. I bought the sensor from the Chevy dealer 6 or 7 years ago after spending a whole afternoon trying to track it down at all of the local parts stores with no luck. I didn't notice any improvement in driveability. When I replaced my engine, I bought an older style quadrajet from JET Performance, and never looked back.

If it runs okay as it is, I would just leave it. If it doesn't, I would consider replacing it with an older style quadrajet or an Edelbrock carb.

Slonaker