Having a problem. OBD1 Code 43

[TechnoLoGs]

Second time losing this post. I am not losing this post again.

Super short version:

1991 Blazer. Code 43
first OBD1 vehicle/problem
Does Code 12 handshake, gives me Code 43
Did this before I melted coolant temp sensor, as per thread in General Forum

Questions:

1. Should I put in higher than 87 octane gas? Will that help or not?
2. Could it be something stupid, like a bad ground?
3. Should I change all my plugs and wires and the distributor cap too? I ask because I have them
4. I can't feel any knocking.
5. The code appears to be set, even if i I disconnect the negative for 30 minutes, it will start up with it off, then come right back on. Help?

 

[TechnoLoGs]

The Internet conenction stabilized. I lost the post, twice, before getting it submitted.

Should I change my plugs and wires?
Should I find and change my knock sensor?
Should I run gas higher than 87?
Are these reasonable places to start for with this code?

 

[DutchBrad]

When I Googled OBD 1 Code #43, it shows it is a ELECTRONIC SPARK CONTROL (ESC) CIRCUIT issue. I would start there. Here is more detail:
CODE 43
Trouble Code 43 indicates that there may be a malfunction in the Electronic Spark Control (ESC) circuit. ESC is used to sense spark knock (pinging) and retard the timing to eliminate it. The knock sensor is located at the rear of the engine block. The ECM will retard the timing by as much as 20 degrees in 1 degree increments. A loss of knock sensor signal or loss of ground at the ESC module will cause the signal at the ECM to remain high. The ECM will act as if no knock is present, and
may possibly result in engine damage, due to detonation.
Code 43 is set when:
? Voltage at Knock Sensor is above 4.8 volts or below .64 volts.
? Either condition is met for about 10 seconds.

Possible causes:
1. Open or shorted knock sensor
2. Loose knock sensor
3. Excessive mechanical noise within engine
4. Improper or incorrectly installed MEM-CAL in the ECM or defective ECM
5. Intermittent open in the EST line to the ignition module

Good luck.

 

[eljefino]

When I had that happen in a saturn S-series OBD-I it was the ignition module itself.

Back-story, back in the 1980s when they were inventing computers the "main" computer would seize control from the distributor/ignitor/module when said main computer felt like it, when the RPMs were over 400. There's a "bypass wire" that gets, IIRC, 5 volts, when it's ready. If the spark computer never hears from the ECM it'll happily spark along just with a safe, retarted program. (If you had a computerized carb it would run as the carb itself would work as a fail safe. TBI would not run without injector pulses.)

Get yourself an honest to goodness Helm shop manual for this thing on ebay, should be around $30.