experts HELP : spark knock

85 caprice with 305.

spark knocks just before a downshift after a turn, or when starting to pull a hill.


running premium gas, new EGR, timing is perfect according to mechanic. New plugs, rotor, wires, cap, have had distributor control module tested, its good.

any ideas on what to try now? would leave it at the mechanic, but out of $$$

thanks for any help

Knock sensor, ESC module, or wiring between them. Have you checked all of these?

where are the knock sensor, and ESC module located?

i would be glad to check them, since now i know they exist. this is my friends car and i dont know how much more whining i can stand:disappoin

Knock sensor is on the passenger side of the engine block, at the block water jacket drain, in the middle of the engine above the oil pan. It has a single wire attaching it, running frontward toward the computer wiring harness behind the alternator.

The ESC module is located in a bracket on the passenger inner fender that also contains the BARO sensor. It has 5 wires on it, one of which ultimately goes to the knock sensor (that wire I talk about above).