Detonation problems

[Talamascan]

Hello all, I'm an ex 300zx owner oozing over from the J30 forum to see if anyone has some ideas about detonation issues with my VG engined J30. After an OEM injector replacement (via the dremel method) the car runs great in all respects except one, namely it now pings in mid throttle applications. Iv'e eliminated the injector, vacume leaks, the MAF, bad ground wires, gas or plugs, and it's probably not an 02 sensor because I have no check engine light, which leaves me looking real hard at the knock sensor.

In this regard, the following quote is from the Z1 site:

"A diagnostic trouble code 34 generated by the ECU means that the circuit for the detonation sensor is broken, not that the ECU has "heard" detonation. The ECU is always looking for a resistance in the detonation sensor circuit of around 1 mega-ohm. If this resistance is not present the ECU throws a code 34 and also goes into a self protection mode in which ECU switches to more conservative safety maps with less timing and more fuel as well as lowers the boost level on Twin Turbo models by opening solenoids that normally bleed off some of the pressure to the wastegate actuators. The faulty part in the detonation sensor circuit is usually the sub-harness between the sensor itself and the EFI harness."

In my case, I'm getting quite audible detonation, but the ecu has NOT switched to a richer map, meaning that if the knock sensor is the culprit, it's not the harness (because the 1 mega-ohm resistance is apparently still present).

So my question is has anybody here encountered a situation where the problem was the actual "microphone" itself? My guess is, if the microphone goes deaf, then the ecu simply has no idea what's happening and does nothing to attempt to prevent the detonation yes?

And, if that's the case, it seems that all I need to do to temporarily alleviate the detonation until I can install a relocated sensor is disconnect the harness, yes?

Thanks

[nissanfreak12]

How is your timing? Are you at 15° BTDC or whatever the J30 is supposed to be at? You can adjust it at the CAS, and if its advanced or retarted it will cause a knock issue.

[Talamascan]

Before changing out the one bad # 3 injector a week ago, the car had never knocked once as long as I'd owned it, and it's unlikely that the timing belt moved somehow, but it's definately worth a check this weekend. It's also unlikely that the knock sensor decided that this was THE perfect time to act stupid as well, but I'm running out of ideas. BTW, checked the fuel pressure last night and it's normal.

I'm curious to see what happens when I disconnect the knock sensor harness. If the ecu does NOT switch to a rich safety map, I'm going to be mighty stumped.

[Talamascan]

Timing is spot on.

Disconnected the knock sensor circuit over the weekend and lost 30 hp, idle went to 2k and the car generally ran like crap, so now I know what the safety mode feels like (and, of course I got an ecu code). Unfortunately, the engine still pinged even in this mode, only the pinging changed from mostly during mid -throttle inputs at speed to mosty pinging right off the line. In order to get the car to stop running the safety mode, I had to disconnect the battery.