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Engine Knock Thread

15K views 161 replies 15 participants last post by  jayochs 
#1 ·
Ok, I needed to make a new thread, since my old one was mainly about my tune, which I thought was making my engine knock but it only exacerbated the problem.

Pretty much, I got an MPT Performance 87 tune as I wanted to keep the car running 87 because well, the 3.7 was made to run regular, and now in NJ with this ridiculous 12% gas tax, i'm in no mood to be paying almost $3 a gallon for 93.

So I got my MPT tune and I noticed the engine would always knock in low rpms when giving it gas. it's a quick little CLONK sound. i have no idea if it's pre-ignition, or spark. I ran data logs and everything, sent to MPT, and I had 4 revisions done, and they all knocked exactly the same. I'm over my month period since getting the tune, so I doubt they'll help anymore, but pretty much if these 4 didn't fix it, they can't fix it because it obviously has to be a problem with my car.

i thought it was the tune, but when i went back to stock, i realized i could SLIGHTLY hear it when shifting. not always, not 100% of the time, but it was still there. the tune exacerbated it because, i believe, the increased throttle response would allow for more throttle at lower rpm's when i shift, thereby pushing the engine and making it knock more than it did stock..that's my theory anyway.

MPT's response was stop using 87, try higher grades, and if that fixes it, that's your problem. that was a lot of people's responses, too. they also said to try quality gas stations..problem is, the only stations by me are Wawa (which apparently is crap, who knew, i always used it..), Lukoil, and Sunoco.

so i tried 93 from Sunoco. it knocked slightly (3rd gear is always the culprit, when I shift into 3rd in my neighborhood around 20-25mph and give it gas as i come out of the shift, it would knock) and SOMETIMES it did it with 93, but even when i slammed gears hard at low speeds, 93 didn't seem to really knock.

which brings me to this: the 3.7 was made for 87; hell, so is the 5.0. why in gods name does MY 3.7 require 93 in order to like 98% stop knocking? i mean hell, it didn't even 100% fix the issue.

i'm not getting a CEL saying my knock sensor is bad or anything, i don't think there's any issue, but i have no idea. again, idk if it's preignition or spark. I've got a video if anyone wants to listen and see what their opinion is; i've already spoken to both Volt and VIG about this, and Volt's even looked at my datalogs and we haven't come to any conclusion. the sound i hear to me sounds identical to when you don't give the car enough gas from a standstill when you're letting off the clutch and the engine starts to knock.
https://www.youtube.com/watch?v=IAk7iTiGqgs
In this video, at exactly 9 seconds, you can hear the first knock when I shift into third..it's after the sound of the shifter going into gear. then skip to 53 seconds, and right after i go over the speedbump and shift, you can hear a loud knock. it's like a clanky CLONK sound. it's weird.

https://www.youtube.com/watch?v=DylFSDrjxgk
in this video, goto 39 seconds. i'm purposely doing crappy shifts because that's when i can always reproduce it. you'll hear it shift into 3rd, then clonk.


Problem is, if I put it back to stock and bring it to ford, i guarantee when they goto drive it, they won't hear it..because even I barely hear it on stock, but it's slightly there. i can't bring it there with the tune, which they would 100% hear, so is my only recourse to bring it to a shop i trust with my tune on and ask their opinion? i don't want to ruin my engine, and i don't want $450 to have gone wasted with this tune.

is this something that could potentially be alleviated by colder/warmer spark plugs, or something? i'm not a gearheard so unfortunately i'm not well versed in any of this.
 
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#103 ·
I'm such a lazy pos though, guys. hahaha seriously though I do appreciate it. one day I'll drive somewhere. I mean hell, I already met ol vig once before so who knows.. but of course he chose to be fancy that day in his Cadillac instead of his stang ?
 
#104 ·
how's a knock sensor value of 3.35 sound? drove a bit today on normal 87 perf tune, and was getting a max of 3.35. heard the sound a bunch of times. this is a higher knock number than on the V4 tune. is that pretty high? still on the regular 87 gas, trying to waste it lol

at 3.25, my rpm was 1957 and speed was 22, so i was probably shifting into 2nd there. hmm

at one of my lower values of -1.25, speed was 32, rpm was 1352...so i don't get it haha
 
#106 · (Edited)
You also need to look at load and throttle. At 1352 that's pretty low into what I'd say third? Any throttle will create a high load in which its ADDING timing. This is good. This is something you want.

Yes the other would more than likely be shifting in second but it's not all just about rpm (speed is pretty irrelevant). What was the load? Throttle actual? Advance?

I agree with volt. I believe you are confusing spark and rod knock. If the sound you are hearing (which I seen the video) was rod knock you would have a piston rod on its way out and a new engine going out. Trust me...I've had it happen.

THIS is audible rod knock. https://www.youtube.com/watch?v=2t6AWqHHLUI

Audible knock will occur in the exact same way pretty much every time and will be in line with the crank shafts rpm not the cam. Yours is not doing that at all.

Mine has started to make a small noise at shift. Nothing unbearable just drive train noise. Either driveshaft or the main shafts in the mt82 which loves to wiggle.
 
#107 ·
that poor stang. why did he want it to blow up? lol. yeah that's excessive knocking.

when I run stock and v4 with stock spark advance the knock hardly ever happens. only on this tune does it really make the noise. it's quite odd.
 
#121 ·
Because there really isn't any going back at that point. It comes from an overly worn rod bearing (Usually from running low oil), and the only solution is tearing the entire engine apart and rebuilding. So many people will go out in one last hurrah when it happens. I know I did with my 3000gt.

When the engine is done for, might as well finish the job! :thumb:
 
#109 ·
YES. that's the exact sound.
 
#110 ·
sometimes it's as long as that when I start off, and sometimes it's just a quick little knock when I just give it gas.
 
#114 ·
mine does it more frequently when its warm yeah, but i heard a small knock on the cold engine the other day. but yeah the say it was like 70 here every single time I gave it gas, it made the noise. then I switched back to stock spark timing tune and it stopped. so it's def related to the tune for me somehow.
 
#115 ·
Well I feel like it may not be the tune because mine does it and mine is all stock.

I am going to get under my car and see if some bolts from the exhaust are hitting or the heat shield on the exhaust manifolds.

It annoys the crap out of me. One of us just need to take it in and see what they say lol
 
#116 ·
Might be rambling but it doesn't make sense that it's engine knock, like real engine knock, because if you just slowly let out the clutch without gas the car will start moving and it doesn't make the sound at all. You would think it would right?

To me it seems like something is just loose and rattling, I suspect either the heat shield, exhaust somehow, or just the transmission noises.
 
#117 ·
no idea. mine doesn't do it when I put better gas in it... so... i doubt higher octane gas makes my heat shields rattle less ?

---------- Post added at 04:10 PM ---------- Previous post was at 04:10 PM ----------

but def go under it. my big *** can't fit under the car fully with ramps on, and i haven't jacked it up yet. so you should go do that and tell me what you find! or bring it in lol
 
#118 ·
Remember what i said before, rubber and other bushings will be less compliant in the cold. In the heat, they will become more compliant and pieces will be more inclined to move around. Doing installs around here there have been times where parts dont quite fit and we need to throw rubber bushings in the freezer for a few hours, or hit silicone couplers with a small propane torch (like for creme' brulee).
 
#119 ·
creme brustang.

yeah i really hope it's something knocking around that can be fixed. i'm on 36 miles left before i need gas! i'm draining this bad boy. can you tell i don't drive often or far for work? lol...i'm gonna do a tank of 91, see if the 87 tune knocks, but mainly bc i really want to try out my 91 tune finally.:dance:
 
#120 ·
Do some logs and let us see them when you run the 91.

Myee_pks said:
Might be rambling but it doesn't make sense that it's engine knock, like real engine knock, because if you just slowly let out the clutch without gas the car will start moving and it doesn't make the sound at all. You would think it would right?

To me it seems like something is just loose and rattling, I suspect either the heat shield, exhaust somehow, or just the transmission noises.
If it was rod knock it would be repetitive in certain RPM's and match your dash RPMs. That's what I was pointing out, that it isn't rod knock. An overly worn/damage rod bearing isn't going to just knock once at shifting. I'm suspecting transmission. Mine does it a small bit when i shift as well. Personally seems more like the transmission main shaft slop making noise as it is quite pronounced through the shifter when shifting.
 
#122 · (Edited)
put 91 in.. put 91 tune on.. holy knock city batman! made a video I'll upload soon of me purposely going through all gears at a low speed, bogging, so the sound is extremely loud. doesn't do that on stock or even the 87. 91 must have even more advanced spark timing. flashing 87 tune back on now, with the 91 in the tank, to see if it does it as bad. my guess is it won't, but who knows! I'll upload some stuff shortly along with a little quick datalog showing 91 on 91 tune to see if i get some knock sensor stuff on it.

*edit*
alright here's the video:
https://www.youtube.com/watch?v=dV7Z7vdZ4hw&feature=youtu.be

everytime gas is given, you'll hear a knock. as gas is constantly given, the knock constantly occurs. don't sit and tell me i'm bogging the engine; I know i am. i went through every gear quickly to blatantly show off how loud the noise can be and how constant it can be. in normal driving, every time gas was given, i'd hear a few knocks until RPM's got higher and it would stop knocking. this is again 91 gas from sunoco on the 91 performance tune from MPT.

when i tuned back to the 87 performance tune with the 91 in it and did exactly above, i would only get 1 light sounding knock the second i gave it gas, and even flooring it in a high gear didn't produce ANY knocking sound.

the gas is clearly changing it. the lower the spark advance is, and the higher the octane gas, the less knocking i get.

i'm sorry, but there's no way this isn't some sort of engine knock. it doesn't sound like rod knock like above, but this has a more knocky sound, like i always describe as two pool balls knocking together. this isn't vibration because the car is vibrating at the exact same rpms on the 87 tune as it is on the 91 tune. now that i've got someone else here on the forum who has the exact same issue as me, i hope the two of us can somehow work together and if one of us brings it in and Ford determines what's wrong, the other can goto their dealer and explain what it is. luckily his does it on stock real bad, whereas mine only does it badly on tunes.

here's the datalog showing a max knock val of 5
https://drive.google.com/open?id=0B26x3Ho6M4AmQkhhSWlFT3lQRUk
 
#127 ·
i'm sorry, but there's no way this isn't some sort of engine knock. it doesn't sound like rod knock like above, but this has a more knocky sound, like i always describe as two pool balls knocking together. this isn't vibration because the car is vibrating at the exact same rpms on the 87 tune as it is on the 91 tune. now that i've got someone else here on the forum who has the exact same issue as me, i hope the two of us can somehow work together and if one of us brings it in and Ford determines what's wrong, the other can goto their dealer and explain what it is. luckily his does it on stock real bad, whereas mine only does it badly on tunes.
No one was ever doubting it was "some kind of knock". We can clearly hear that it is. What is being speculated on is the cause of it. Half the issue is that video can be extremely deceptive sounding, or it can miss many of the frequencies that are being emitted. Such as the video you just posted I have a hard time really hearing what it is over the exhaust/wind lol. Part of me hears a knock the other part hears sandpaper lol.

Take a listen to this video. https://www.youtube.com/watch?v=6xTWHJADFe8
This is what it sounds like when spark knock occurs. This is even on a ford motor. (5.0 to be exact) It's more like marbles in a can, not a knocking sound or a "pool ball" sound. I think what most people are concluding to is it sounds like a mechanical issue not a pre-det issue.

To reiterate VoltWings Number 3 point, you're really not in the realm where you should be having pre-det anyways. When I look at your log I see nothing showing you SHOULD knock. Low load, Low RPM, Low speed, No advance, not even hard throttle angle. There's nothing here that would point that it could be possible unless the fuel/tune is just that bad. To me that points to mechanical.

Honestly I feel like we're all just going in circles at this point. I would just bite the bullet and take it to a shop and have them ride with. They will be able to diagnose much better than a video on youtube brother.
 
#124 ·
yup, and it seems to get worse when spark timing is advanced with these tunes.
 
#126 · (Edited)
believe me, i am, and i'm considering trading it in for something else. i'd love to just trade it towards a '14 GT or something, but at the same time, i'm saving to buy a house, so it makes no sense to put down money and start another loan.

look, i can put 87 in it and put the stock tune back on, but at that point, it's calling a $450 loss on a tuner i have no need for anymore because i can't use it, and even then, i still get slight knocking on stock! so wtf.
 
#131 ·
so advanced spark means what else is moving though? do you have a thought as to what it could be if it's outside the engine?
 
#130 ·
#133 ·
wish i had a gopro. believe me. i'd suction that thing to the hood to get a nice loud sound of it, but i don't have 400 bucks to blow on a good one right now.
 
#137 ·
volt did suggest a compression test, but i'd have to bring that somewhere to do. after looking into it, i'm not that mechanically inclined.
 
#138 ·
That's more of failsafe in my eyes. Spark knock wears the piston rings. Worn piston rings = loss in compression. Granted a knock that just started may not have damaged the rings yet but over time it will. How loud your's is... if it showed lack of compression i'd be more inclined to say it sure as hell sounds like they forgot to install the rings all together :p:
 
#139 ·
bah!! stupid car. makes me mad because literally nothing in my life can ever just be, ya know? lol theres always an issue with any of my major purchases.
 
#140 ·
I know the feeling brotherman, I am still trying to work through mine although luckily mine isn't audible and I'm about 95% sure it's false. Getting my new GT500 exhaust Tuesday to help keep the noise down, and have them check to see if it's causing the issue. I see a ton of LTH/OR X's causing this issue.
 
#141 ·
keep us updated with yours too!
 
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