Kurt Crosbie

I'm not sure whether or not i put in the lt4 or the lt1 module. The one sitting in front of me is part number 16188309-1084348.

I'm getting code 43 and I'm guessing its for that reason. If its not for that reason then i'm screwed becuase I don't have a volt meter to check the voltage on the harness to the sensor or on the sensor itself. How much do these tools cost?

RansZ28

LT4 knock module 16214681

1racerdude

I have tried the LT-4 KM on several different cars with false knock and it did nothing for them,still had retard.
If you are sure it's false knock,get the resistor from Radio Shack and install in line with your knock sender.This will fool the computer into thinking it has no knock.
Ya can find it on the board with a search and instructions to install. This subject comes up often in hot weather and mods headers,RR's,cam,rattling exhaust,anything that makes more noise than it originally came with.
Or get it tuned out of the computer,but with the resistor ya can take it back out for NO charge, It is only a couple of bucks.

VintageMuscle

Yep...putting an OBDII sensor that monitors 2 sensors into a OBDI car with 1 sensor is a mistake in my opinion, yet often recommended on this site because it's "less sensitive". Just because it's stock on an LT4 with RR doesn't mean it's less sensitive....that's a myth.....

Re-installing the original LT1 KM into my 95 cured all my hesitation and stumbling problems. It was knocking with the LT4KM, but stopped knocking with the LT1 even though I'm running Crane RR and Edelbrock shorties...

Also, I find it funny on the hesitation/knocking strings where everything else is recommended.....except a new, correct, knock module.

It's cheap/easy and worth a try in your OBDI car...and you'll find you can add timing back in that you've bend pulling trying to cure that knockin...and you'll run better...

Kurt Crosbie

When you get an lt4 km, do you have to tune your computer for it? Cause I just want to put my lt1 module back in.

Are you saying that going back to the lt1 km should cure the code 43?

Kurt Crosbie

If your computer detected false knock, what code do you usually get?

Injuneer

There are no codes for "false knock". Just means the knock sensor "heard" a noise, sent a signal to the knock module, the knock module filtered it and passed on the remaining signal to the PCM. The PCM saw the "knock" and retarded the timing. Neither the PCM nor the knock sensor has any way to tell if the noise came from "true" knock or "false" knock (note - there is some "tuning" in the piezo microphone used in the knock sensor to make it more sensitive to the frequencies the represent true knock, but its not a very selective tuning).

The "module" is a filter. The LT4 module is specifically designed to recognize the noise signature from the full roller rockers used in the LT4 engine, and to selctively filter those noises out of the signal that goes to the PCM. The LT4 KM will "filter" (not "less sensitive", just "more selective") the roller rocker noises, since that would provide a "false" knock signal. But there is no guarantee that the LT4 KM will filter all sources of false knock.

I think there are far too many of us with OBD-I, single knock sensor setups, who have taken the time to test the LT4 KM and its response to true and false knock, and found it to work correctly. The fact that the LT4 has two knock sensors does not appear to be a factor. So did the LT1 C4. Who knows what the PCM does with the knock sensor signal before it passes it to the KM? Its extracting the alternating frequency signal from the 5V carrier (pulled down to 2.5V) and processing that, not the complete knock sensor output. There's an interface between them.

chuckd4more

How does the PCM programming by desensitizing the knock module work for this application? Will this accomplish the same goal or are you better to go with the LT4 KM?

Injuneer

"Desensitizing", whether in the PCM or in the knock sensor/circuit, reduces the PCM's response to knock. It reduces that response (retard) whether its hearing true knock or false knock. Bottom line is, you are losing some protection against detonation.

Using a "filter" like the LT4KM appears to be a safer approach, since it isn't less sensitive, its more selective. It will not reduce your protection from detonation, and may help eliminate false knock. But it can't cure all "false" noises.

If you think about it, many years ago there were no knock sensors, and people actaully "listened" for knock, or checked the spark plugs regularly. The knock sensor just reduces the need to do this. I don't run a knock sensor.... it would be a problem with a noisy solid roller camshaft. But I have a lot of dyno tuning to back up the setup, and use fuel out of a barrel that I know matches the fuel it was tuned for - not really practical for a street driven car.

chuckd4more

Thanx Injuneer. I am going to rebuild with Lloyds LE2 setup so I guess I will remember to change to the LT4KM at that time.

Kurt Crosbie

Could the fact that I'm runnning hooker lt's and and x-pipe with no cats or mufflers have anything to do with this? Or the fact that my exhaust beats on my floorboard when I hit the gas? Could excessive banging and other noises throw the knock sensor off and make the pcm think that it is bad?

Injuneer

Check your motor mounts. One of them is right next to the knock sensor, and could obviously affect it if the mount was rattling. You can also get spurious noise signals in the knock sensor harness from nearby high voltage (e.g. plug) wires. Something that bangs on the chassis or the steering shaft might possibly affect the sensor. I don't buy into the loud exhaust being a contributing problem, but some people claim its has caused false knock.

I've also seen a case where someone pulled the knock sensor out and found a ball of RTV stuffed in it and affecting it.

Kurt Crosbie

Ok, so then the banging exhaust and motor mounts could cause the pcm to throw a code because of excessive noise....

1racerdude

ANY noise other than the noise it was programed for will trigger retard. The LT-4 module won't help...

Kurt Crosbie

And excessive retard will throw a code 43, right?