In the process of changing my front Y pipe last week, I found that the lead to the Knock Sensor had become disconnected ( it was laying on the little tray that seems to protect it from gremlins).

Good chance it has been disconnected for two months (last time i changed oil)

Now that I reconnected it, and along with the new no cat front Y Pipe, I am getting a spark retard on acceleration.

Reading the HELMS, it seems to indicate that if knock sensor is disconnected, no codes are thrown (I got none), but since the ESC module is trying to send volts to the knock sensor, can it be damaged by the disconnect?

There was a thread here a long while back, which I tended to regard as so much :bs , about knock sensors going bad and reducing performance.

Now I am wondering?

It has been suggested to add a couple of degrees to advance as a result of installing straight Y pipe, which I will try.

But just curious what you have experienced with this circuitry! This is the only circuit I have found so far that doesn't throw codes when it is not complete and may actually inhibit performance if it is complete.

The straight Y Pipe is noisier than the pre cat pipe and I am also wondering if this additional noise could be setting off the knock sensor?

Sorry if this is long! but this is not as simple as my emergency brake handle problem :D

:seeya

:steering:


[Modified by jackdaroofer, 8:14 PM 1/7/2004]

 

If you are sure there is no mechanical cause such as metal to metal clang causing false knock replace the ESC module.

Mine was causing false knock a few years ago and I upgraded to the model recommended by Gordon Killebrew which solved the problem. Details are on my site, link in sig. below.

 

When I bought my 85 the wire going to the knock sensor was burned and not hooked up I didn't even know what it was but fixed it .........no codes...the GM manuel says it will ether keep the spark normal with no retard or add full retard all the time...great which is it? so I pull my haynes manuel out and it says it will do nothing or add full retard :crazy: I don't know any more after reading both manuels, but I guess if it runs better with it hooked than its retarding you....mine didn't run any better that I remember and if it was retarding 27 degrees or what ever you'd notice. now that I'm supercharged and its retarding me I'm rethinking the hole thing....looking for a lt4 knock senser :cheers:

 

Lead Foot.....GREAT looking motor :thumbs:

Now back to the original topic. :)

 

,I've read in a couple of books. written by guys who seem to know what they're talking about, that some knock retard is normal for they type of system it is.

When the engine is first started the ECM checks that circuit and if you read a startup trace you should see one or two knock retard counts listed.

I don't believe the ESC module is damaged when the knock sensor is disconnected.

You can always check to see if it does NO retard or FULL retard by running a scan program. I've just never done it. About the limit I've go to was to install a resistor in the ESC line to fool the ECM into thinking the knock sensor was connected and working; I know that little trick works.

Jake

 

:cheers: Always good sound advice :thumbs:

I have bookmarked your web site, I'll be back :D

Thanks

:seeya

:steering: