Have a 1991 base model w/new water pump, 150k miles, rebuilt trans, runs hot like most do, was sitting in traffic as usual and saw SES light come on and temp start rising, pulled out of traffic and started to move, noticed lack of power, had to step far down on pedal to speed up. Got it home and checked codes, noticed H43. Disconnected and reconnected knock sensor wire (L98 rh side only). and SES went out, cleared code and drove around for about an hour, light came on again just slowly accelerating, with engine temp about 215. Took it home and let it cool overnight. Started it and still had SES on. disconnected connector from sensor again, sensor checked good for continuity and wire good for voltage, cleaned with "Deoxit" and reconnected. Started engine, SES light off and no code. What I noticed is that the wire to the connector is VERY tight, and plastic black wire protector has disintegrated off the wire, so wondering if it could be separating from connector when it heats up, or maybe holding on by a few strands. Also, I have a new wire to replace it, and new sensor if needed. But looks like I need to remove the starter to get to the wire. Anyone had similar issues with their wire being too tight? Is this a design issue with this year? Do I need to drop the starter to get to the wire to splice in a new one??

 

Well you need to fix your high temp problem. High temp is what is causing the detonation in the chambers. The knock sensor is just doing it's job by pulling back timing and your slow throttle response verifies that.

Just because the WP doesn't leak doesn't mean you don't have cooling problems. Once you can verify your cooling temps are reasonable with your temp gauge then you should look elsewhere at the excessive knocking.

 

Thanks for the info. I filled the tank with what I thought was 92 octane Speedway gas not long before the issue started. Also got the AC running recently (additional load on engine). The car has run these temps since I bought it 3 yrs ago without issues. So I will also double check the initial timing, maybe add some octane booster ( Speedway may have put 87 octane in the 92 pump) , change the oil and coolant, and drive without the AC for awhile and see if that helps, while keeping a close eye on the temp. With that many miles on engine, could be timing chain, lifters, piston slap (oil breakdown), AC compressor, leaking plug wire, computer, original knock sensor acting up, and maybe other things?? Just wanted to hear what the most common fixes have been.

 

Woow, your shooting from the hip at everything. First you originally said temps were rising while sitting in traffic but now you claim those temps are normal. That now means the engine temps are normal but now your pulling a DTC. What you need to do is get some hard facts what is really going on wrong with your motor then maybe we can help you.

150k miles is only mid life for the sbc bottom end. Top end looses valve seal and the cam looses lift but will run on with reduced performance.

Now the metal timing chains do start to loosen while the older sbc had a nylon cam gear but that would not normally live to 150k mi so I don't expect you have a nylon one.

AC compressor and leaking plug wire are just to far out there to talk about.

I don't know if a 1991 has a ESC module but if does you need a test procedure for the knock senor and the ESC. In other words you need a maintenance manual and a multimeter to troubleshoot this.

Good luck.

 

Thanks for the info. The '91 has the ESC module is in the ECM.
Today I reset initial timing to 6 BTDC, (checked it and found it was only at 2 BTDC). Also replaced the RH valve cover crankcase breather hose rubber grommet, which I thought might have been leaking, and replaced the PCV on LH side, just to be safe.
Then I added an octane booster, just in case i got a tank of 87 octane thinking it was 92. Let it sit in 76 degrees in the driveway idling for 10 minutes and temp gage stayed above the halfway mark. Drove it around for 15 mins the car seems to have a little more "pep", and seems to run a little cooler now. I hear no odd sounds coming from the engine. If there is an ESC problem, it is intermittent. I'm still not sure what triggers it? Anyway, think I will look for a used OBD1 scanner to help me watch what's going on. and enable me to follow the trouble shooting instructions in my FSM.

 

UPDATE>>>>>>>>>>>>>>Problem Solved!!!!!!!!!
I dropped the starter a few days ago to check the knock sensor wire, and sure enough, the black plastic wire loom had disintegrated and there was a 1/4" long bare spot on the sensor wire where the wire was probably laying against the top of the starter motor and grounding out. (Check the simple logical things first!) Replaced that (about 10") of wire with a new connector w/pigtail wire I bought, put double plastic heat proof wire loom over it, connected it to the old knock sensor, and it is running great again, actually better than it has in the last few years.