formul8

This is in a '94 Corvette.

Left bank is running very rich with a little black smoke from that side at idle, smoke screen at WOT. The CEL comes on after the engine warms up. It struggles, idles likes it is going to die out and then the CEL comes on and it idles fine again.

Code H43 comes up, which is "knock sensor circuit". The CEL light will go off after a while and then sometimes reappears.

The opti has 1,500 miles on it and is a OEM part. New plug wires, plugs and knock sensors have been installed in the last 1,000 miles. The car has 53K on it.

Someone on another website forum said this is the opti going out, but I don't think that is the case.

Any ideas?

hey01

what about the knock sensor module on the ECU

Rising Phoenix

Or the sensor itself? It's in the side of the block, passenger side I *think*. Maybe one of the wires got burned or cut or something.

Injuneer

The knock sensor codes sets when the voltage on the circuit falls outside the range of 1.5 - 3.5V. Sounds like you may have a loose wire, a bad ground at the sensor, or a failing sensor. 43 is not related to the knock module in the PCM. The F-Body PCM sets DTC 47 for the knock module, but I don't see that code in my 94 Corvette code list. Pull the wire off the sensor (doesn't the Corvette have two sensors?) and check for 5V with the key on, measured from the single conductor wire to an engine ground. Shake the wire while testing, in case its an intermittent "short" or "open". If the wire is OK, check the knock sensor. With wire still off, measure the resistance between the single pin on the sensor and the block. Should be in the range of 3500-4500 ohms. Finally, connect the wire to the sensor and measure the voltage between the wire and ground. Has to be in the range of 1.5 - 3.5V.

If its running as rich as you describe, surprising that 43 is the only code you are getting. Running excessively rich on one bank can be cause by exhaust leaks before the O2 sensor, misfires on that bank, faulty O2 sensor or wiring, incorrectly adjusted valves.

Also, where does the vacuum compensation line from the fuel pressure regulator connect on the Corvette LT1. If its on the left side of the manifold (right side on the F-Body) it could be leaking fuel into that side of the manifold if the pressure regulator diaphragm is broken.

Any mods on the engine? Why not add a "signature" with basic info about your car, year, model, tranny and any major mods?

sbs

That is the prototypical description of a bad O2 sensor.

hairbear21

If it does turn out to be the