I was under the car changing out the positive battery cable and saw this:

Attachment 167369

Help me out here. Where does it go? That is the back of the starter you are looking at just in case anyone was wondering.

 

that looks like the connector for either the knock sensor(located on the side of the block in front of the starter) or cooling fan temp switch(if equipped with electric cooling fan)

 

Ditto....looks like one of those two.

 

Is that a knock sensor behind the tip of the thumb?

 

It's indeed for the knock sensor, you can see the sensor is not hooked up, just next to your thumb.

 

Thats new to me What does the knock sensor do? and what years of trans ams are equipped with them?

 

All GM EFI systems have a knock sensor (even the computer controlled q jets have them), basically if your car has a EST controlled HEI, it has a knock sensor.

Anyway, it's sort of a microphone and is used by the ESC (electronic spark control) to "listen" for characteristic accoustic signals indicating detonation (the knock sensor is engine specific, they are not all created equal). The knock sensor is hooked up to the ESC, basically an interpreter/amplifier. This signals the ECM in case of knock and then the ECM tells the ESC to back off the timing until the knock is gone, the EST then starts advancing the timing again.

 

Ok that would be why i dont know about it, I have only had plain Q-Jets.

 

IIRC, 85 up had the sensor. Unsure about the Canadian cars.

JamesC

 

Yes, when they upped the LG4 compression to 9.5:1. L69's all had it.

Only L69's, and as I understand, the later LG4's (like '86-'87) finally had the CC carb. But, if not CC, no knock sensor (I believe).

 

if the knock sensor is broken or unhooked will you be able to hear knock or ping under hard acceleration?

 

 

It depends how bad it is. When I had my timing at 10, it would pull a little timing when I stabbed the throttle. Never heard a thing, but the knock sensor did.

 

i think i need a new timing chain or something, my car knocks or pings i dunno whats what haha, my timing was 2 or 3 degrees retarded when i got it and i put it to 0 should i go higher maybe? i read somewhere tbi's like a little more timing?