I have an 88 Firbird which has a knock underload after the engine is warmed. There is no code. I have tried to test the knock sensor by watching the timing as I tap on the intake manifold with a samll hammer, but the timing does not change. How can I troublshoot the knocksensor and ESC with a voltmeter?? Or am I stuck with just changing parts??

 

You can't see the timing change - it changes too quickly. And the knock sensor wouldn't pick up noise from the intake anyway - it's looking for detonation in the block/heads. I'd replace knock sensor, they are cheap enough.

 

In case you didnt already know,be careful before you just yank the knock sensor out.Its in a water jacket and will leak coolant when removed.If the sound is only under load my guess,without hearing it,would be an exhaust leak.

 

...not to hijack your thread but I'm having the same problem. I've been chasing this detonation/knock for over two years. I changed the injectors,fuel pump,FPR,computer,tps,sensors,iac,egr valve,timing is 6 degrees, run 89 or 91 octane.

I even discounted the knock sensor yesterday and it still knocked/pinged under load...can't figure it out, some days it won't ping/detonate,other times it acts up. The only thing I didn't change was maf but don't think that's the issue....what else can cause this??

any help on this thread would be great.

 

Mine was doing it pretty bad one time.Turned out it was the ignition coil.I was running MSD coil and it had a crack in the plastic tower where the plug wire plugs in to go to the distributor.It was jumping spark out of it to all kinds of stuff,but you couldnt tell it tillI saw it in the dark.