Does the 3.1 v6 have a knock sensor? I just finished the rebuild on my firebird and it starts on the first crank every time but it seems to be running very rough with a lot of vibration. it also seems to be missing through all the rpm range. Before you ask, heres what i know...

1. Good oil pressure (50lbs at idle)

2. Good spark to all plugs

3. Timing set correctly

4. All injectors are firing and none are clogged

5. Vaccum is a little low and somewhat erratic (although i do have a hotter cam)


The only reason i ask is because i can see what looks like a connector for a knock sensor (oval shaped white plastic, 1 wire connector going above starter) I dont see a hole for it, but then again maybe the machine shop plugged it? I do see a few fresh plugs dripping with gasket sealent?

Sorry for the dumb post

 

On my 305 theres a knock sensor right under the fan switch, both of which are directly above the starter

if theres a hole thats been plugged thats about 2" in diameter thats probably it

 

But lack of a knock sensor wouldn't have any affect on the normal operation of the engine. The engine can work without it. It would only work against you if you were under heavy throttle. The engine will start to ping, and if you didn't back off, then it would throw a code shortly after. So unless your rough-running condition includes strong pinging, then your lack of a knock sensor isn't likely to be your problem.

 

It could have something to do with your low vacuum. Vacuum is related to EGR. And EGR can cause rough running. So it's probably not a coincidence.

And to answer your original question about whether or not your V6 should have a knock sensor, my repair manual shows that you don't have one.

 

Yes, the 3.1 has a knock sensor. It's the large round one-wire sensor screwed into the bottom of the block near the starter.

I think it's unlikely the sensor could be the cause of your problem BUT...... here's a way you can know for sure:

TEMPORARILY deactivate the knock sensor by running the wire instead through a 3900 Ohm resistor ($.25 at Radio Shack) and then on to a good ground, instead of connecting it to the sensor. This will trick the ECM into thinking it's still there (no check engine light) but, obviously, it will never register any knock.

 

Well, my Haynes manual has been wrong before, lol. But I know your knock sensor isn't the problem because my knock sensor wire was broken for about two years before I discovered it. The engine will run perfectly without a knock sensor--unless it begins to ping under heavy throttle.

Mine never got bad enough to throw a code until I moved to the mountain area and had to drive UP them to get home each day. I crawled underneath, and there it was--the wire was broken and hanging there. It had probably been broken since the first time my starter was changed. It was then that I gave up on mechanics and began working on my own car.

 

That's odd. If you simply disconnect the knock sensor the ECM should throw a "Check Engine" light immediately after startup when it sees the resistance to ground across that wire is infinite instead of the ~3900 Ohms it should be. At least it did on my 91 3.1L V6 Camaro.

 

Ok i got it. There is a knock sensor and i already put it in. Thanks guys



Mods- please remove this thread as it is no longer any use, thanks!