Okay, still tracking down my knock retard issues.
I have been running the LT4 KM for years and never had an issue with KR on my old all bolt-on LT1.

On my current engine (see sig) the KR is wildly out of control all across the board. It averages 4-5 degress all the time.

For the fun of it I re-installed my original LT1 KM and the KR is totally gone across the board except for high RPM WOT, then it goes to 5 degrees retard. It is totally obvious that either my LT1 KM just works better or my LT4 KM must be fried and gives false readings galore.

Anybody ever have an LT4 KM go bad?
Anybody ever have their LT1 KM work better than the LT4?

 

do you have the right knock sensor to go with the KM

 

I was told that the sensors were all the same, I have seen it on the board both ways.

So is there a different sensor?

I am positive that I do not have the two knock sensors mixed up.

 

The LT4KM works with either the OBD-I or OBD-II sensor. But the PCM requires a matching sensor.

Have you checked it for codes? DTC 47 indicates a faulty or missing knock module. I'd suspect if you have that code, the PCM will start to provide almost continuous knock retard, as a function of engine load, RPM, etc. That's what it does when the knock sensor sets a code (DTC 43).

 

Judging from the above statement I am asuming that the same sensor is used for both KM's.

Nope, never had a code like that with the LT4 KM. I am OBD1 BTW.
Currently I am running a parts house knock sensor, not the GM. Maybe I should put the GM in and try that.

I am still thinking the LT4 KM is fried.

 

The knock sensor has to match the PCM - OBD-I or OBD-II. That's what the sensor connects to. The module is further along in the processing chain than the sensor, and does not appear to interface with it.

I know your 95 is OBD-I. You need a 4.5 Kohm sensor, and if you had the wrong one, you would already have DTC 43. If you were OBD-II, you would be using the 100 Kohm sensor. Some people think that because the LT4 used an OBD-II PCM, the LT4KM will only work with the 100 Kohm sensor. That is not correct. You can use either the 4.5 Kohm sensor, or the 100 Kohm sensor, as long as it matches your PCM.

 

Just for the fun of it I will get the resistance off the sensor. So where do I go from here?

 

i had similar issues when i installed my long tube headers. i took the sensor and put a couple layers of teflon tape around the threads to de-sensitise it. i dont know if thats a good idea or not but, it took away all of the knock. just make sure you run premium fuel.

 

Update:
I got another NIB LT4 KM. The readings less than WOT are somewhat better with this module than the suspect one, although still not rock solid zero like my LT1 KM. The WOT reading are much better with the new module, most of the time zero but sometimes around 3 or so. I think this proves that my old LT4 KM is busted.

It seems to me that the PCM is staying in "recovery mode" longer than really needed when the knock sensor picks up some noise, it also seems like the knock retard just hangs around when cruising interstate speed in 6th gear too.

I also purchased a Delco knock sensor to install, the one I have now came from a parts house, maybe that will further help.

I find it wierd that when less than WOT the LT1 and the LT4 KM's react differently, I guess i would expect similar readings in this area.

 

If you are getting no knock with the LT1 KM, why not stick with it?
I've had the LT4 KM start giving me screwy results and went back to the LT1KM also on my truck since it has a '95 OBD1 PCM... but my '95 TA I finally gave up trying to find the cause...switched KM, PCMs, sensors, could never get it to go away. Put in race fuel, same amout of knock....so I reprogrammed the PCM to remove the "Burst Knock" and changed the recovery time to almost 0...now it will get a few degrees at WOT and quickly recover to 0. Mine would go for miles with no knock...then one WOT blast would see a little bit and then it would constantly remove 3-4 degrees even at cruise...simply irritating. I feel most of the issue was with the burst knock maybe from the larger cam....I don't know for sure but programmign it to 0 pretty much resolved the issue... Guess I'll know when I put in the smaller LPE cam this fall.

 

Rob,
The LT1 KM gives me 5 degrees KR all the time at WOT. It gives zero KR nearly all the time at less than WOT. I am sure that that I will eventuallt tune it out like you suggested, I just want to use that as the last resort.

 

Update,
I just installed the Delco knock sensor and my KR is now as bad as ever even with the new KM. Clearly the Autozone sensor I removed worked better, therfore I guess it will go back in.
I will also try my LT1 KM one more time with this new sensor.

I installed the new sensor with teflon tape and light torque as suggested but I guess I will continue to chase down the gremlin. It now looks like I am even one step closer to tuning the dang thing completely out.

 

Bummer, it absolutely drove me bananas. I didn't like tuning out the knock either by reducing the knock retard capabilities..but after a while I've forgotten about doing it..except when I read this I'm hoping it all had to do with this big azz cam and the burst knock...going to cam swap in a few months. I've got a LE1.5 cam on the shelf, but felt the idle would still be too rough for the wife, so I'm putting in the LPE 211/219 first as it works very well in the truck.

 

I used to get knock retard out of my *** until my tuner fixed it. He sped up the recovery and limited the knock retard to 4 degrees, and I can go monthis without any getting KR.

 

Everyone check out this link for the resistor mod:
http://www.charm.net/~mchaney/knock.gif

Does this really work or is it dangerous?