Knock sensor guru needed.

[Scooterwrench]

I've done the 1227747 to 1227427 swap on ol Smoky and after about 30sec of running the SES light came on. I wasn't surprised, was actually expecting it. The later ECM uses a 3900 ohm KS and haven't found a resistance value in the 91 FSM for the sensor that is in the engine. Finding a 3900 ohm KS is not a problem but I wanted to install the KS in the back of the right head so does anybody know of a 3900 ohm KS with a 3/8"-16 thread?

 

[scott2093]

and haven't found a resistance value in the 91 FSM for the sensor that is in the engine

see if code 43 (ESC) troubleshooting shows it for your truck

just looked at 91 manual and it only has 3300-4500 ohms listed for trucks with 4l80e..
doesn't mention value for other models....

 

[Scooterwrench]

see if code 43 (ESC) troubleshooting shows it for your truck

just looked at 91 manual and it only has 3300-4500 ohms listed for trucks with 4l80e..
doesn't mention value for other models....

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.

 

[scott2093]

Yes, it was code 43.

It's unclear why, in the manual , it shows a recommended value for the ks in the code 43 troubleshooting but only for the "with 4l80e" trucks. The other ones have a somewhat different troubleshooting tree unless I looked too quickly and one could assume the 3000-4500 ohms is the recommended value of the ks for all of the models....

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

Any chance to hook up a real scanner to see if it's telling you the same story?
Only reason I say this is because I'm seeing stupid knock counts using aldl droid and I'm certain they have to be imaginary but I need to verify with my scanner to be sure. Even then, I'll need to dig further to see who's not acting right.

 

[Scooterwrench]

I

It's unclear why, in the manual , it shows a recommended value for the ks in the code 43 troubleshooting but only for the "with 4l80e" trucks. The other ones have a somewhat different troubleshooting tree unless I looked too quickly and one could assume the 3000-4500 ohms is the recommended value of the ks for all of the models....

Any chance to hook up a real scanner to see if it's telling you the same story?
Only reason I say this is because I'm seeing stupid knock counts using aldl droid and I'm certain they have to be imaginary but I need to verify with my scanner to be sure. Even then, I'll need to dig further to see who's not acting right.

I think I've got you confused. I'm running a 1995 ECM in my '91 truck that supposedly came out of a '95 van. In the '95 FSM it does give a resistance value of 3900 ohms. I'm just trying to find a GM vehicle that ran a 3900 ohm KS with a 3/8-16 thread or part# for 3900 ohm KS with a 3/8-16 thread so I can bolt it into the back of my head.

 

[scott2093]

I

I think I've got you confused. I'm running a 1995 ECM in my '91 truck that supposedly came out of a '95 van. In the '95 FSM it does give a resistance value of 3900 ohms. I'm just trying to find a GM vehicle that ran a 3900 ohm KS with a 3/8-16 thread or part# for 3900 ohm KS with a 3/8-16 thread so I can bolt it into the back of my head.

I see... Is that a smaller port than where it usually goes? I'm guessing any kind of adapter will throw off the response... moving it from it's original location probably brings enough of that into play?

 

[PlayingWithTBI]

^^^This - I wonder if being in the head so close to the actual detonations of the cylinder(s) will skew its accuracy.

 

[n2xlr8n]

^^^This - I wonder if being in the head so close to the actual detonations of the cylinder(s) will skew its accuracy.

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.

 

[Scooterwrench]

I see... Is that a smaller port than where it usually goes? I'm guessing any kind of adapter will throw off the response... moving it from it's original location probably brings enough of that into play?

I reckon I could chuck it up in my lathe and re-cut the threads from 1/4 NPT to 3/8-16.

 

[Scooterwrench]

^^^This - I wonder if being in the head so close to the actual detonations of the cylinder(s) will skew its accuracy.

Yeah,I wondered about that too. Maybe read more spark knock and less rod knock?