knock help

[LETZRIDE]

So I can't for the life of me get rid of the knock in my car...I got anywhere from 1-14* knock virtually on about 85% of my histograms. Fueling is fine for the most part, timing goes all the way down to 4* under knock conditions...I'm down to 15*-17* spark timing in my octane table in some known areas, and nothing seems to be working. I for the life of me can't believe this is real knock...but maybe it is.

I happens under all three conditions, accel, decel, and cruising.

When I was double checking things at idle today I could hear a faint knocking sound, but I also saw the platform for the coil packs rattling off the valve covers...I tightened that down, but I still hear a bit of a knocking sound (sounds like a vibrating knocking) coming from somewhere. I can't for the life of me find it, and the fact that everything on the car shakes so damn much with this cam, its not making things easier lol.

Can a vibration like this cause me to get false knock? if so, I don't suppose wrapping the knock sensors in dynamat would help any? Especially if its something knocking against the engine?...I just honestly can't see anything else that might be knocking around...

[3.4grapeofwrath]

Re: knock help

I noticed in my car every time I would pull up next to a drive through window at a fast food restaurant I could hear this slight knocking noise. I guess with the window down and being close to the wall it would amplify the knock. I also had a vibration at idle so I disconnected the torque converter to eliminate the trans from the picture, to my surprise when I started the car there was a very loud knocking sound coming from the engine, it was an obvious rod knock. When I reconnected the torque converter it went back to a slight knocking sound.
I guess the converter acts like a noise dampener. I ended up replacing all the rod bearings.

[LETZRIDE]

Re: knock help

motor has 4,000 km on her, and when we looked at it before it went in...everything looked good...

the vibration knock will happen at idle after you rev it a bit...then it will appear after the rev for a little...then you can rev it a bit again and it wont be there, but then it will be there a few seconds later. Sometimes You dont hear it at all...I think its something loose somewhere...but I have no idea where, like I said...everything shakes with the new cam

[whitdog54]

Re: knock help

desensitize the knock sensors, these 3.8s get tons of false knock. Thats why the newer 3.8s make more power. They upped the timing because they got rid of false knock.

Although the fact you can hear it knocking is what makes me think it might not be.... you cant even narrow down the area its coming from?

[LETZRIDE]

Re: knock help

somewhere from the back of the engine it sounds like...but is sounds more like a vibrating knock then the knock I heard when I spun the bearing...like picture something banging off a part of the motor...I thought it might be the coilpack bracket, but I tightened it down as much as I could...doesnt look like its vibrating...but the damn car vibrates so much it rattled the nuts loose lol...I saw the front one turning itself

[Bird_Of_Prey]

Re: knock help

What do you have your idle set at that it shakes so bad? 500RPM?

[3.4grapeofwrath]

Re: knock help

Check the flexplate/torque converter bolts. Will cause vibration and knocking if loose.

[LETZRIDE]

Re: knock help

What do you have your idle set at that it shakes so bad? 500RPM?

850 when it's warm...1200 when its cold

[LETZRIDE]

Re: knock help

is it possible to tell if its false just from looking at how it appears in the scans?

[Bird_Of_Prey]

Re: knock help

I doubt it's false if you're getting it all the time.

[LETZRIDE]

Re: knock help

if you look at the scans its so random though...where it gives you knock at one point, it wont do it again at that exact same point next time...alot of the time its under part throttle conditions to...like 15% tps...

If its caused by a vibration it will happen all the time I think...and I dont think desensitizing the sensors is going to help if this is the case...

[Meemperor]

Re: knock help

Call Kevin! (416) 863-TUNE :)

[LETZRIDE]

Re: knock help

that means someone else has to tune!...

[ssms5411]

Re: knock help

desensitize the knock sensors, these 3.8s get tons of false knock. Thats why the newer 3.8s make more power. They upped the timing because they got rid of false knock.

Although the fact you can hear it knocking is what makes me think it might not be.... you cant even narrow down the area its coming from?

Thats what my Dad always told me about the KR sensors on the 3800's , so I desentized mine 40% and haven't had any problems, will still pick up real KR which is great. But like you say if your hearing it , its probably a problem somewhere.

[LETZRIDE]

Re: knock help

I cant get under the car right now...but I am almost wondering if its the exhaust or something rattling under there...that type of knocking vibration I think is still going to cause knock whether I desensitize the sensors or not no?

Steve, do you mind taking a quick peak at my scan? tell me what you think about the knock Im picking up, and the patterns it occurs?