I seem to have a little knock right off idle when I snap the throttle.
It sounds like pre-ignition but thats the only time I here it.It doesn't do it once the RPMs are above 1000 or so,only when I snap the throttle from idle(around 600 RPMs).
Also I don't here it when I'm driving,only when I'm under the hood.
The plugs have less than 8000 miles on them and look fine aside from a little carbon build up.I just changed the cap and rotor because there was some corrosion and build up in the cap....
The car runs great but this knock is driving me BATTY.

So I guess my question is,could this be the ESC?
Does the ESC just go out,or are there symptoms first.....
Thanks,Brian

89 GTA,L98,lt1 cam blah,blah,blah.
And the timing is set at 6*BTDC...

 

It's more than likely the knock sensor starting to go. If the ESC was going, then the car would be surging and missing.

 

Thanks,
Do you know if there is any way to check it or monitor it?I do have an AutoXray.

 

As far as I know, the ESC just takes the signal from the knock sensor, and converts it to useful informataion theat the ECM can interpet, and retard the timing.

So I don't think it's the ESC.

Knocksensor? Ya, could be bad...not detecting the knocks/pings you're getting, but the knock sensor is not causing the the knock/ping...it's there for when it occurs.

I'd start with backing off the timing a few degrees...maybe down to 4*BTDC.

There's a plethora of things that cause off idle pinging, high combustion temps, timing, carbon deposits, vacuum leaks, etc...best to look into those instead of a failed component.

How high is the engine coolant temp when it occurs? Does it do it on a cool (160-170) engine too?

 

The engine only has about 8000 miles on it,and when I ported the heads I even knocked all the sharp edges off the combustion chamber.
The car rarely runs over 190* even in bumper to bumper traffic in the summer.
It has only been doing it for about a month.No codes either.

 

When my knock sensor was dying it didn't through any codes either. I just replaced it and the knock disappeared. Same timing.

 

I sometimes get one barely audible knock on a fast throttle tip in before the detonation sensor picks it up ans starts to adjust the timing. Actually, I think it only does it when the idle is really low and temperature is rather high (200°F).

 

Thanks for the responses guys.
Anyone have the GM part # for a knock sensor on a 89 L98?