Knock sensor tests? Ohms, Voltage, etc...

[ILIKESHELBYS]

87 GLHS Charger.

Besides giving the intake manifold a few raps with a hammer while the engine is running and watching for the timing to retard briefly...is there any other test for a knock sensor?

I have one on the car that is less than a year old, it measures about 3.8K - 4K ohms and I have a used one on the bench, it measures 20-40 ohms...a huge difference.

Any idea what resistance/ohms a known working knock sensor should measure or even if that is a valid test?

...or what voltage should I expect to read across the sensor (terminal to ground I guess) with the engine running?

[detobias]

its a piezoelectric sensor, it generates a voltage when excited

it would be a very brief 'spike' ; I think you would need an oscilloscope to see it

[ILIKESHELBYS]

Yup, that is exactly what I was thinking...I sold my oscilloscope too soon I guess. If someone had a spare laying around or even one on the car and could give ohm or across the sensor voltage readings that might help us to establish a baseline. Ill measure the voltage across mine today as well as try the bang test and post the results.

[UnaClocker]

You MIGHT find some useful information in this thread. But it's way beyond what you're trying to figure out, so you'll be digging through a lot of other information if it's in there at all.

[ILIKESHELBYS]

Una: I read through that thread, not at all over my head since I have an almost complete electronics engineering degree (all be it 20 years old) but amazingly enough, not one word about how to test one that you already have. :-(

[UnaClocker]

Mmm.. Well in that case find some more used ones.. Go with whatever you find most of them doing.. ;)

[JDre]

The bang test is valid, retards the ignition timing a moment. If that works on your car, sensor is good. The other sensor is shorted out. Odd. Mine always fail open, just hear pings with 94 octane all of a sudden. I went to measure mine, but the connector plug is stuck! And now, an unrelated starter problem has appeared! It's still the same old Lancer.

[ILIKESHELBYS]

UNA: ROFLOL
JDre: Thanks for the insight...and Murphy's law in action...regrets