Spark advance issue

[LT7A]

Originally Posted by ChevyTech

Has it set a code 43?

Here is an example of a hard to find code 43 I ran across.
This truck would set the code under heavy acceleration at freeway speeds.
I helped a friend of mine from an import dealer fix a code 43 a several years ago. His code started setting after installing a crate engine. After six months at two Chevrolet dealers and an import dealer, nobody wanted to work on it anymore. The circuits had been tested by several people and my thought was a mechanical knock was causing the problem. The decision was made to tear down the engine. Removing the oil pan revealed the problem. The metal baffle in the oil pan was broken loose on one side. Under certain conditions the loose baffle would rattle and the knock sensor would detect it as pinging.

Low circuit voltage on the circuit from the ESC module to the ECM for longer than 5 seconds is the other criteria (for 1989 C/K1500 350 auto) to set a code 43. When the baffle would rattle for an extended period of time, the timing would back down, the knock sensor still detected at knock the module would lower the voltage on the circuit signaling the ECM it detects a knock.

My point is, if something is loose or rattling it can cause this code, and every test in the manual won’t find the problem.

A rattle or a knock anywhere on the engine or transmission can cause the spark advance to be pulled even if it is not bad enough to get a code 43 to set.

This is good info. Thanks for taking the time to write it out.