ok heres the story. TPI 355, commander 950.

I have the knock sensor, and bless its little module, it works.

problem is, it works too well. it picks up a TON of knock in the strangest places.

for instance, if i go anywhere past 18* of timing at idle, it picks up knock and drags me down to freaking 10*. causes the idle speed to go nuts of course.

and if i stab the gas, it picks up a ton of knock. when im driving down the road at a constant speed, say 40 MPH, light load, it should be able to handle at LEAST 35* of timing, heck i was running 45* before with the carb, but it picks up knock and retards the timing to freaking 22*... adds it back in... gets to 28*... retards it more. very very super sensitive i guess.

Now since its commander 950, i have the power to adjust decay rate, add in rate, total retard etc... so ive sort of "disabled" it by putting 0* retard during knock. the engine runs great now, of course, since its not being retarded (pun intended) but i WANT the knock sensor to work, and detect knock.
WHy is this thing picking up so much false knock? the cam isnt THAT big, and its not THAT rough. im wondering what could cause such a thing? I read somwhere wrapping the sensor in teflon would make it less sensitive, think its worth a shot? what else can de-sensitize it?

 

How tight did you turn the knock sensor? If it is too tight it will read faulse knock.

 

Yeah, try to loosen it a little and see what happens. Also you can wrap the threads in teflon tape to deaden it a bit.

 

Is the knock sensor new? When did you start having the problem?

 

What octane of gas are you running?
Whats your compression ratio?

 

Do you have the correct sensor? GM has two type of sensors one 100 kOhms and och one 3.0 kOhms (i think) they changed it when they changed to MAP........

Did the Holley come with a sensor?
Whats the base timing set to? make sure its 6 deg.

/n.

 

<b>How tight did you turn the knock sensor?</b>
Good idea ill losen it today
<b>Also you can wrap the threads in teflon tape to deaden it a bit.</b>
Ill do that too...
<b>Is the knock sensor new?</b>
Brand new, this is the first time running the motor with a knock sensor or even EFI for that matter.
<b>What octane of gas are you running?
Whats your compression ratio?</b>
9:1 compression, blower pistons. aluminum heads. shouldnt have ANY problem with timing. with the carb i was running 45*-50* on the highway. now it wont let me run more than 23*. darn thing.
<b>Do you have the correct sensor? GM has two type of sensors one 100 kOhms and och one 3.0 kOhms (i think) they changed it when they changed to MAP........

Did the Holley come with a sensor?
</b>
The holley did NOT come with a sensor, i picked up one for a TPI car, a 350, but didnt specifiy MAF or MAP... Maybe i will go get a new one, for like a 92 MAP car, plug it in with teflon and see what happens.

<b>Whats the base timing set to? make sure its 6 deg. </b>
WHy does that matter? i have the base timing set to wherever i want because the holley has a "base adjust" right now its 7.
on the spark map i have 17* of timing at idle set in.

Its surging like crazy too because it will pull out timing then add it back in this raises and lowers the RPMS like 300 every four seconds. very very annoying, and not only that, the extra heat from the retarded spark caused the plug wire to melt all over the headers and ground out causing a miss on #3!!!!!

 

The sensor does not need to be that tight. Also, is your exhaust hitting on the frame or anywhere else for that matter? This will cause a faulse knock. Good luck

 

well pulled it out (with coolant spilling everywhere) put teflon on it, and put it in hand-tight (as opposed to vice grip tight)...

and now it works good. it picks up knock like its supposed to, such as on the highway when i was testing how much advance i could give it...

turns out i can go no more than 48* of spark advance before i get some knock during light cruise.

and at WOT im running 38* so far without so much as a .5* retard, so ill probably leave it there..

but on a sad note, the surging continues. i seem to have an intermitten vacuum leak somwhere... very odd. it will idle up to about 1500 rpms, then back down to 1000 rpms, whenever it feels like.

thanks for the help, im glad the knock sensor is working like it should.

 

Your going to need to get intouch whit Holley and see which sensor they require. The MAF knock sensor was 100k, and the SD one was 3.9k ohm... thers a huge difference there.

Thing is, Pep Boys and a few other auto parts store computer systems DON'T know that there are 2 different sensors, and will give you the 100k one. Ask me how I know lol. I couldnt imagine what my SD ecm was thinking when the new sensor was giving it 100k ohms worth of knock when its only used to seeing 3.9. :sillylol:

 

There is also a 305 SD knock sensor and a different one for the 350 so make sure u have the right one.


Also i believe the torque spec for the knock sensor is 15ft lb(wont swear but pds it is)

LAter
Jeremy