Knock sensor guru needed.

[Scooterwrench]

Yes, it absolutely will- good catch.

The resonant frequencies and resultant reference tables used by ECM are based not only on the impedance of the KS, but the mechanical position.
A KS mounted on the cylinder head gives totally different respponse to one mounted on the side of the block, for example.

I know GM put some knock sensors higher up on the engine. I never measured the resistance of one to see what it was.

 

[PlayingWithTBI]

I know GM put some knock sensors higher up on the engine. I never measured the resistance of one to see what it was.

Weren't those in the valley's water jacket? Maybe those are balanced between the cylinders?

 

[L31MaxExpress]

Yes, it was code 43. I turned the KS off in the .bin so I could carry on with the datalogging and VE tuning. Apparently I didn't turn something off because I still got knock counts in the datalog. With the KS having the wrong value I'm not sure I should believe what the log is telling me and it is retarding my timing. I'm not hearing any audible ping. I put a more aggressive timing curve than what GM burned in there. 0 initial, 18 at the bottom, 24 in the middle with a 34 max at 6000 and 20 kpa is what I started with and after seeing knock I pulled 2 deg out of the knock zones and smoothed the table again. I need to get a KS with the right value so I can set the parameters back in the .bin and fine tune the advance curve better and I don't want the KS down in the block drain hole. I use those drains when I do coolant changes and would just as soon not be screwing with the KS once it's installed.

I would open the distributor and look at the ignition control module. If it still has the GM module it could have as much as 6° of timing difference at high RPM depending on if it has a 048 or 369 module. A TBI head will only want 26-30° of WOT total timing at high rpm.

 

[Scooterwrench]

I would open the distributor and look at the ignition control module. If it still has the GM module it could have as much as 6° of timing difference at high RPM depending on if it has a 048 or 369 module. A TBI head will only want 26-30° of WOT total timing at high rpm.

Would a faulty ICM cause no data above 4400 RPM? I replace the dist. because the pickup coil was crumbling(but the truck ran good). It came with a new, probably chinese ICM in it. I saved my old ICM and threw it in the glovebox.
It's an 048. Two other issues that may be ICM related are extra ignition pulses showing up in the timing light and a discrepancy in rev limit dialed in and actual rev limit.
This is my open throttle spark table;

You must be registered for see images attach

 

[docstoy]

Didn't the mid 90's model s-10's with the CPI fuel system have knock sensors mounted in cylinder heads ?

 

[Supercharged111]

If you move the knock sensor it will not work as delivered from GM. Too sensitive, not sensitive enough, who knows? I doubt enough parameters are open in that dinosaur of a PCM to be able to get it decently recalibrated. I'd put it right where GM had it if you're hoping to lean on it.

 

[Scooterwrench]

Didn't the mid 90's model s-10's with the CPI fuel system have knock sensors mounted in cylinder heads ?

You may be right, I can't remember now where GM put the KS in the 151.

 

[Scooterwrench]

If you move the knock sensor it will not work as delivered from GM. Too sensitive, not sensitive enough, who knows? I doubt enough parameters are open in that dinosaur of a PCM to be able to get it decently recalibrated. I'd put it right where GM had it if you're hoping to lean on it.

This whole fuel system is not as GM built it. I did stumble across a post over on gearhead where someone was explaining how to change the .bin for going from dual sensors to single sensors. Something about changing the supply voltage to the KS.
After crawling up under there this morning and seeing where the KS is located I may want to move it when I put the 355 in with long tubes.

 

[Supercharged111]

This whole fuel system is not as GM built it. I did stumble across a post over on gearhead where someone was explaining how to change the .bin for going from dual sensors to single sensors. Something about changing the supply voltage to the KS.

It's not about the fuel system though, it's about matching the knock sensor and its location to the software that accompanies it in the PCM. Having a different intake manifold or fuel injection setup has no bearing on the KS ability to detect pre-ignition.