My motor in the 93 isn't the original... It is a 4.3 Vortec W series. I need to know where the possibility of a second knock sensor may be? The one located between spark plugs on the driver's side is new. New plug too. I don't know where an additional (if that's the case) is located. Also, the book says something about a engine spark control module behind the block, but no diagrams... Is that the module in the distributor? If so, that's new too! My truck has an erratic idle. At first, code 43 showed itself at stop lights... But when I accelerated, it would disappear. Now it's constant, and idle problems... Any help? Thanks.

 

I beleive you have a knock sensor on the back down below the distributor too, I have never touched mine... But im sure I have read threads about them on here and there is 2 on the W engine. That code doesnt necessarily have to be a fault of the knock sensor or spark advance controler, loose rocker arms and torgue convertor bolts and anything loose and rattling can set the code 43 off too by sending a false knock sound through the engine. Ive never had it happen to me but I read alot online about these things.

Yes the spark module is in the bottom of the distributor.

Also, the W (CPI) engine IS the original engine for your 93. Its what most of us have. I think there is also a Z (TBI) engine, but not as many, and the W is much more powerful than the Z anyways.

Im sure one of our blazer gurus will chime in here soon on the info on your second knock sensor and some tests you can do.

 

Back of the passenger side cylinder head.

 

I did hear something about a flow chart to diagnose this code and problem step-by-step. Anyone else have this procedure(?)as it is not in the Haynes. @ OhSoFly: What I meant to say is that I believe this motor was swapped from a Camaro. Another thing: I wish there were some way to disable the ECU from adjusting timing upon receipt of a knock signal. Even if it's a little engine noise, it's affecting the way my truck runs by adjusting my timing automatically.

 

The 2nd knock sensor, which stood out like a sore thumb when I finally spotted it, is UNPLUGGED. The plug end is damaged. I'll go pick another one up today! Thanks guys.