About that knock sensor...

You tap on the side of the block near the sensor and see if you get a signal or see if the timing retards.

Ahhh, now, how do I measure engine timming changes? :)

Well thats the thing. I've almost always had access to scantools and looked off of them. However, when you tap it and you hear a change in the engines rpm it might be retarding the timing.

Hmm. I could plug my oscilloscope into it, if I knew where. I have a timming light but I don't think it'd be too useful since the timming seems to jump around anyway. Though i think that's just the pulley bouncing. I'll try that first though if I can.

Has anyone heard of a sensor failing in a way that it'd cause the engine to retard the timming, yet not turn on mr trouble light?

It's said that other noises can make the knock sensor respond. One example given is a squeaking belt or idler pulley. The sensor "hears" that and, mistaking it for a knock, retards the spark. Listen around the engine compartment for unusual noises.

A scan tool is probably the best way to detect retarded spark. It will also tell you other things that could be just as significant as spark.

Bob Henry

I'm not sure if they retard timing if they fail but they can fail without turning on the MIL. Actually that might be possible... I havent fooled with knock sensors in some time. But you should be able to tap on the block next to the sensor and hear a audible change in the engine as it adjust timing.

I could see possible scenarios where it COULD do it. i.e. it's got the engine convinced you're pinging all the time or whatnot.

This motor for quite a while now has almost NEVER pinged, even in places/situations where it used to when new.

And, retarded timming suggest bad mileage to me. And maybe high HCs.

I know nothing about them, other than they're supposed to be like a microphone. There is a squeaky pulley on the car, but I can't figure out which one it is :(

I'll try that. I don't know how I can get near it easily, though.