The Example

I had a post on "SES light on 91, car is sluggish". I finally pulled the codes and got a code 43, the Knock Sensor circuit. The light comes on intermittently, and a few times it stayed on constantly. Today I took it for a drive and the light came on after I accelerated. Yesterday the light was on intermittently, and then it went on constantly and the car felt very sluggish; any gas past 1/2 throttle and the car would fall on its face. What is going on?!?

bogus

when the sensor goes off, it will retard timing... upto 20 degrees or so. this will cause death in performance.

the 1991 has a module on the side of the header box on the passengerside of the engine compartment. that part, the Electronic Spark Control, may have died... the other option is the sensor itself.

The Example

If that is true, it is good news! I did notice that performance was decreased with the light on, but it could have been my imagination. How much does a new ESC or sensor run, and what is involved in replacement?

onedef92

The AC/Delco sensors (which I recommend) run about $35 to $40 apiece. You can get aftermarket ones a little cheaper, but they MAY NOT be calibrated to your ECM's specs and can also throw Code 43.

Before you do a voltage test or replace a sensor on a hunch, remove the heat shield or shields (LT-1 and LT-4 engines have TWO knock sensors) and simply clean the sensor's electrical contacts with a shot of WD-40 or electrical contact cleaner.

In some cases, grease and grime degrade the electrical signal from the sensor to the ECM and throw Code 43.

Clean your contacts, disconnect your battery for one minute to clear the codes and restart the engine, if no Service Engine Soon lamp comes on and you have no other ECM issues, you know you've fixed that problem!

If you DO have to replace the sensors, the orange tape that coats the screws of the unit is sufficient to seal the sensor back in your block. Do NOT use threading tape or compound sealant.

Also, tighten the sensor with a TORQUE WRENCH to 14 to 18 foot lbs. or you will have the same problems. Knock sensor torque is critical here. Too much can over sensitize or damage the sensor and too little can render it useless and unable to protect your motor from potentially harmful engine knock!

Good luck and keep us in the loop.

The Example

All right, I am ready to check out the sensor, but where exactly is it? Do I need anything special to get to it like a ramp?

MTVette

Stormy, looks like you and I have the same recent problem, a code 43. Look at my thread on this part of the Forum.