I have been working on my friends car for the last week installing a nitrous system on it. Now that i have it installed i plugged in diacom just to find out that his knock sensor was going off already without the NOS
Any way the only way i seem to be able to get rid of the knock is to set his timing to 4 deg after. Thats right After!!! it is losing a lot of power. Anybody know what the problem could be. Can A knock sensor go bad like that?
Thanx

Oh yea its a 91 GTA 305 almost stock
with Brand new plugs and wires
the mixture looks pretty good too
Hangs right around 128 blm

 

Sounds like the sensor has gone bad or it's picking up false knock in the motor. I would lean towards the false knock. Can you hear any unusual sounds around the motor, ie, rod knock or a noisy lifter?

 

Nope im not hearing any of that it sounds great besides the loss of power
but I thought the knock sensor would retard the timing before I heard anything.

 

After you set the timing to 4 degrees after TDC, did the knock go away completely?
If so, then it ain't false knock.
Another test you can do is drain the tank, then put in a couple of gallons of 101 unleaded race fuel and see if it continues to knock, if not, then its not false knock.
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If it continues to knock, was this motor originally TPI? I ask because I did the TBI to TPI switch on my truck, and it detonated all the time and was not false, whatever I tried it didn't work to cure it.
I verified it was not false by removing the knock sensor and grounding it to the frame, then I could hear the detonation/pinging.
Turns out that the TBI cam in my truck is different than the TBI cam in the f-bodies, and the lobe separation is way too small for TPI, like around 104 degrees, TPI really needs at least 112. Anyway, a new cam is in my future. In the interim I have had several people take stabs at custom programming the timing curve to make it work for now, and the knock sensor is temporarily disconnected as now I do have false knock from the rod bearings, the detonation was too much for them

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Rob
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Leaving the knock sensor disconnected, would that make the car run like ***t? The reason Im asking is I wanna run the gear drives for the cam and alot of people have said that I might have a problem because of the vibrations sent by the gear drives. Is there a way to somehow bypass the knock sensor? Thanks for any info.

 

Just plain disconnecting the knock sensor will trip a code in the computer and will give you lots of knock retard. You need to hook up another knock sensor that's not in the engine, or I think you might be able to just ground the sensor wire. Anyway, If you do this you have to be really careful about knocking because the comptuer will give you full timing from the tables in the chip, even if you are getting knock. If you let the engine knock heavily, you can cause extensive internal damage (engine rebuild time).

 

As just mentioned above, if you disconnect it, be very certain that you're not getting any knock. You can usually hear it when its above 6 or 7 degrees, sounds like valve clatter / pinging. I would not recommend doing it on a good motor, too risky!
The only reason I have done it is because I have enough rod/bearing knock that its setting it off falsely now, to the tune of 15-20 degrees! So my bearing are already fried so who cares!
Yes, if you just disconnect it, it will set codes, what I did was took a spare knock sensor, (or remove yours and plug the hole as coolant will drain out). Then connect it up to the wire to the ECM, then connect another wire on the threaded part that screwed into the block (use a nut to thread on to it to hold the wire on). Then ground that wire to the chasis.
I wrapped the knock sensor up in duct tape so it still would not get any knock, then zip tied it up to the transmission cooler lines.