Can I emulate a Knock Sensor?

[jmgtp]

sounds silly I know... but my 3.1 still does not run proper! no power at all, so bad that its not driveable. KS is next thing on the list to check. I dont have a scan tool or free access to one. So is there any way I can emulate a "good" knock signal by unpluggin the harness from the KS and sticking a resistor or something in it (its 1 wire so I dont know how a resistor would work for that, but you get the idea!)?

hmmm.... or option 2... I buy a new KS plug it in to the harness and let it dangle in the air (maybe I have to ground it with a piece of wire?) would that work? That way I still have the option to return it should it not be the problem. (on a very very tight budget right now - otherwise I'd have paid someone to put this thing on a scan tool).

[5speedz34]

Well, if you are trying to test a ks what u do is *I think* leave it in a let the motor run and tap the motor by it and it is supposed to change the spark timing or something, you should be able to tell.

[jmgtp]

well I dunno if tapping it will do the trick. Problem is if I have to tap it, that means I'm under the car, which also means its idling. I dont think I'd be able to really hear a difference in the way it runs. Especially if the KS is bad and pulling a lot of spark already. I still think KS is a long shot since this all happened when I changed plugs/wires. I dont know what could have gone so wrong in that 10 minutes that the car went from running strong to hardly running.

a discouraged 3.1 owner

makes me love my dohc that much more. hehe

[RacerX11]

You probably won't hear a difference. You just need to hook up a timing light when you do the tapping, and you should see the timing retarded when you tap.

If this all started when you changed plugs and wires, I would check into that before messing with the KS.

Marty

[jmgtp]

You probably won't hear a difference. You just need to hook up a timing light when you do the tapping, and you should see the timing retarded when you tap.

If this all started when you changed plugs and wires, I would check into that before messing with the KS.

Marty

Ah... a timing light... good thinking.

I have checked the plugs wires a few dozen times over. Even put the original stuff all back in. The wires are definetly going to the write places.

Heres the 2 threads concerning the problem I'm having:

http://www.60degreev6.com/phpBB2/viewtopic.php?t=149

http://www.60degreev6.com/phpBB2/viewtopic.php?t=339

if anyone has any input I'd appreciate it. I have a week off for Thanksgiving break and I really hope I can get this thing together. Its supposed to be my winter/school car so the GTP can slumber in the garage and get some headwork done.

[Homer]

According to the gm service manual that under normal conditions the circuit would measure 2.5 volts, and the pcm only sends 5V to it. Also it says a normal knock sensor has a resistance of between 3.3k - 4.5k Ohms.

[jmgtp]

According to the gm service manual that under normal conditions the circuit would measure 2.5 volts, and the pcm only sends 5V to it. Also it says a normal knock sensor has a resistance of between 3.3k - 4.5k Ohms.

hmmm interesting. I thought the KS used an a/c voltage signal. For the sake of arguement.... lets say the KS was totally bad and the ecm was pulling as much spark as it could. Would this cause the engine to have absolutely no power? I mean none, so bad that in 1st gear at 1/2 to full throttle nothing happens, even slows down. But engine can move the car and maintain speed (sorta) at ~5% throttle but still no power.

[Homer]

The knock sensor wont retard the timing more than around 10 degrees, and if it is retarding the timing a lot for over 20 seconds it will set the check engine light. Also the KS has both ac and dc voltage. Under normal conditions there will just be dc voltage, but when the knock sensor is triggered it creates an ac voltage which "rides" on the 2.5 dc voltage.

Correction; i ment 18 degrees not 10.

[v6h.o.]

it will retard more than 10 degree's.. it was retarding my timing 15 degree's when my wiring went out on me.

i have a 10K resistor to ground on my ECM wiring for the KS, it runs fine like that.
was too lazy to find the short to ground on the KS wiring. so i bypassed it... LOL.