chriseacrett

Recently I installed a set of BC 272 cams and got tuned, my car ran great for about 4 days and then started to run bad. So I started dataloging, and found that in 1st and 2nd gear between 2k and 4k rpm with low load(mostly while turning left) it says that I am knocking like 30-40 times just for a few moments and then it goes away. I could be in 3rd gear and WOT to redline and NOTHING no knock at all. So, I can only assume that I am getting "phantom knock"....


The thing is, I have checked everywhere and everything and cannot come up with any source. My theory is that it could be the clutch, as I have seen that as a source of phantom knock, it rattles really bad when the clutch is engaged(I think its the throwoutbearing). I bought the car used, have put 40k miles on it since I have had it and have no idea what clutch is in it.

Just wondering if anyone has any thoughts on this, or if there is a way that I can tell for sure if its the clutch without tearing the car apart?

MR. Tim

iTrader: (11)

When you say you are knocking 30-40 times, do you mean 30-40 counts of knock, or do you mean a few counts of knock 30-40 times in a row (succession).

chriseacrett

Like single instances of 30 counts of knock, then nothing
Sometimes it will be like two instances of 20 counts of knock then nothing

I think it is ONLY in 1st and 2nd and usually between 2k and 4k rpm and during light load, it used to do it just from reving my engine up to 4k rpms with the clutch disengaged

lemmonhead

i have a feeling phantom knock wont run 40 consecutive 1 counts of knock.I think you really have some sort of problem. to lean, to much timing or something actually hitting something because you say when you turn?

chriseacrett

No, I am sorry...I am bad at explaining things

What I mean is I will have just 2 or 3 times in a row where "Knock Sum" is ~30(20-30) and then it will go to 0, but only during those very specific times, not 30 times of 1 count of knock.

lemmonhead

as far as i know phantom knock will never give ya 20-30 knock sum count. you have some issue, sounds serious also. what is your a/f ratios?

chriseacrett

Well I have seen guys with DSMs get almost 50 counts of phantom knock, a lot of times due to a bad knock sensor and sometimes lifters...

I can say that my fuel injectors tick REALLY loudly. It just seems odd that it would be actual knock because like I said it only does 20-30 counts(sometimes less) like ONCE maybe twice then goes right to 0, and it is ONLY in 1st and 2nd gear ONLY between 2k and 4k rpms and usually ONLY when I am doing less than half throttle, and most of the time when turning left(it doesn't always do it when I just take off strait). I can say that between that rpm range something is vibrating bad as you can feel it in the seat and sometime can hear it.

I just figured if it is still the stock clutch in there the thing would be on its last legs by now, I had to adjust the clutch pedal rather high so that I could shift at high RPMs, and I have seen on here where someone had phantom knock due to a smoked clutch...but just a thought, as I am by no means an expert

Another thing is that I put the ECU back to stock and it still did it, I don't have anyway to measure AFR right yet, but will soon...

I can post a log, would that help?

chriseacrett

Oh another thing...

I was getting the same amounts of knock from just reving the engine, and the spark plug cover was lose and vibrating, took care of that and there has been no trace of knock while reving since, but anyways

steexz

iTrader: (4)

yea i have the same problem, its weird light load between 80-140 between 0-3 psi i can be in neutral rev the car and will get knock... sometimes 35... its weird.. and i cant pinpoint it... pissing me off.

MR. Tim

iTrader: (11)

Just out of curiosity, when you guys are getting this high a count of knock, are you feeling the car hit that proverbial brick wall in acceleration or throttle?

lemmonhead

i still cant fathim how something vibrating could cause such a high knock count, i could see 1-3 but 30-40? someone please correct me if im wrong but from what I understand when true detonation happens it dont just produce one frequency wave propagation right? that is why the more severe the detonation, the more stonger the pressure wave is and more harmonic frequencies there are.
the higher the number the more stong the frequencies and more harmonic frequencies involved. So if you have something vibrating it should only resonate at 1 frequency, it could be loud but seems it should not register such a high knock sum as true detonation.
??

chriseacrett

No brick wall, I had that happen to me a long time ago though, I do know what you're talking about...

Well, I needed some gas so I got some gas but at a different place, a place that had gotten gas at when my car was running good, I also used some fuel system cleaner and then I drove it around a bit and it seems to be going away.

It doesn't spike as high anymore, and when it does count knock it goes to 3-5 but it seems to not be happening at all anymore

So, bad gas maybe?

But I still think the clutch is just about shot

scorke

iTrader: (18)

Heres an idea.


Pull timing, see if it goes away.




If it does, its not phantom, if it doesn't it MIGHT be.

Scorke