I have a problem with the an Opel Astra F, x16sz engine, 1.6 petrol, 1995. Hard start especially when engine is cold and hesitates when in load. When the engine is hot, it runs well. I exclude a fuel supply issue because the car behaves the same on petrol and on LPG.
I checked the sensors with the oscilloscope (engine coolant temperature , throttle position sensor , manifold absolute pressure sensor , crankshaft angle sensor and knock sensor, EGR valve is cancelled with a thin sheet of copper) . All signals are looking good ( compared with those from Autodata , Vivid Workshop and your website database) except the knock sensor. The knock sensor is a one wire type. I have no errors stored in the ECU. The car behaves much better with the knock sensor disconnected (hard start is still there but much better in load conditions).
With the knock sensor disconnected I get approximately 4.5V at the ECU input, and with the sensor connected I get 2.5V (ok, maybe that's why I didn't get a DTC related to knock sensor) .
This is a capture of the knock output when engine is running:
It can be seen the the knock output is biased to 2.5V.
When key on engine off and I lightly knock in the engine block I get similar waveforms but with slightly lower amplitude.
From what I've seen on the net about the signals generated by other knock sensors, their oscillations were much longer than what I have - other sensors had an oscillation duration of a few milliseconds and I have only a few microseconds (1000 times less).
On my engine, beside the knock sensor, the system also includes a knock processor, which, they say, amplifies and filters the knock signal so that the detonation is easily recognized by the ECU .
This knock processor, when there are no detonations, for example when ignition is on and engine off is should output about 10V (according to Autodata and Vivid Workshop ), that's what I have, all ok until now. The moment it detects a detonation, the processor output should pull to ground - 0V (according to Vivid Workshop ) and is easily read by the ECU. In my case, when the engine is running the processor output stays at 10V for the whole engine running time, it never pulls to ground. The wiring seems ok , knock sensor signal reaches the processor and processor output reaches ECU.
Maybe the knock processor doesn't work correctly because the knock signal is invalid? (oscillation duration too short in my case?)
How should a good knock signal look like? Do you think I'm dealing with a defective sensor?