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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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#2 ·
Sounds like a loose heat shield to me. Doesn't sound like detonation (spark knock) at all to me. Good luck :)
 
#3 ·
This. IDK, get under the car and start banging on stuff. Exhaust hangers, heat shields, slop in the driveline (which these cars have tons of)... i mean obviously something is clunking, so you just gotta get under there and start digging you know.
 
#4 ·
really? i don't get it though. at all. because to me it sounds just like the sound when you don't give it enough gas off takeoff, and that's definitely the engine clunking.

you guys really think this could just be something vibrating? why does it do it more with a tune though and seem to go away with better grade gas for the most part?
 
#6 ·
I'm gonna have to make a video of the knock sound when you take off badly with not enough throttle. it's identical to that sound.
 
#8 ·
This lol. You're still confusing "knock" with "a knocking sound coming from somewhere around the engine bay." They are not the same thing.

Its likely a worn mount or bushing. The snappier reaponse of the tune causes the contact to be harder. Thats my thought at least, but with the amount of effort and attention that has been put into your tunes they can clearly be rulled out. Next step is to go under there and see what may be making contact.
 
#13 ·
how would i check those out?

i still have to make a video of the knock sound when you have a bad start and run it side by side from the knock sounds i showed you guys, because seriously, i'm not kidding when i say the sound is identical which is why i feel it's inside the engine.
 
#15 ·
hmm ok i'll look into it. i still have to youtube different knocking sounds to see if mine sound like any.
 
#17 ·
110% positive it's from the front. the rear issue i had was it squeaking when it was cold out.
 
#18 ·
https://www.youtube.com/watch?v=JA0cH_vRABg

guys, hate to say it, but his knocking sound is identical to mine. that's exactly the rattling/knocking around sound i hear, but it doesn't last nearly as long as his and is only quick like 2 or 3 knocks.

one thing i noticed when watching videos though, there's a video of a guy with his volvo who was getting the issue, and he tried a million things and nothing helped, and he said in the end he suspected too much air getting into the intake thereby making it run lean or something, creating the knock. he ended up thinking it was a leak or something, and he replaced a part that fixed it, so proper air was getting in..
what i'm getting to is i wonder if the airaid modular intake tube has anything to do with it? i assume with it being a straight tube, it lets some more air into the engine, but they say you don't need a tune or anything for these...but i wonder if maybe my engine just never compensated for it? when i first installed it, it took a lot longer to start the car up, but maybe that's bc i disconnected the battery..i don't remember. i wonder if i've got an issue with it and should try to take it off and reinstall it?
 
#19 ·
https://www.youtube.com/watch?v=JA0cH_vRABg



one thing i noticed when watching videos though, there's a video of a guy with his volvo who was getting the issue, and he tried a million things and nothing helped, and he said in the end he suspected too much air getting into the intake thereby making it run lean or something, creating the knock. he ended up thinking it was a leak or something, and he replaced a part that fixed it, so proper air was getting in..
what i'm getting to is i wonder if the airaid modular intake tube has anything to do with it? i assume with it being a straight tube, it lets some more air into the engine, but they say you don't need a tune or anything for these...but i wonder if maybe my engine just never compensated for it? when i first installed it, it took a lot longer to start the car up, but maybe that's bc i disconnected the battery..i don't remember. i wonder if i've got an issue with it and should try to take it off and reinstall it?
1. The point of having a maf is for it to compensate for airflow. As long as you do not change the diameter of your MAF sensor housing, which you did not, you will not need a tune; the computer can compensate on its own. Assuming you installed it correctly.

2. Assuming you do have rod knock, and assuming you do not want to get under the car to inspect it may be anything else, look up how to do a compression check. A compression check may indicate if one cylinder is in fact causing some issues.
 
#21 ·
nope, still knocks after putting it on/off. going to try one last tune revision i forgot i had that i never tried yet.
 
#22 ·
so in the 4th revision of the tune, mpt dropped the spark timing down to stock. in doing so obviously the car is slower than it would be with performance norm tune. so, if it's truly stopping the knock like this, could this be a spark plug issue? mike from mpt was nice enough to suggest the following :

Based on that alone, I’d reset several things.

OEM plugs at OEM gap, clean the maf sensor, do a complete carbon cleaning such as sea foam.

*

your thoughts? I took the maf sensor out and it didn't look corroded or anything. I've never used sea foam and i haven't ever checked the plugs on the car before.
 
#23 · (Edited)
Its possible for a spark plug to go bad but I've read you should get a CEL saying 'misfire' on the bad cylinder. I run a 1/2 gallon of gas with sea foam in my 40 year old 2 stroke boat motor once per year. Some people swear by sea foam, some people say its 'snake oil' and doesn't do anything. I say it works but I've never used it in a car :)
 
#24 ·
Definitely do the suggested plugs and gap and clean MAF. They built the tune for the stock plugs and gap. We have over 60,000 on our horse and picked up a cel, cleaned MAF, cleared code and every thing is fine now. We run MPT tunes in our 3.7, have had no troubles at all. Love their tunes.
 
#25 ·
i love the tune too, but i just get the knock. i did the 4th revision tune which dropped spark timing to stock, and the car feels so much slower again, it sucks. i want that V1 tune back, but if I do, i'll get knock, and i don't want to hurt my car.

the MAF looked fine, how would i actually clean it? and unless my plugs are bad at 20k miles, idk why else this would happen. i looked into how to check the plugs and it really looks like such a pain in the *** on this car. my haynes manual shows you have to remove the whole intake manifold to get at the one side. ugh
 
#26 ·
Go to the parts store and get MAF cleaner, there is directions on can of how clean your sensor. Pay attention how it came out[ which way the wire faces]. Do Not Touch Wire! Do you have the stock plugs in your car? Did someone re-gap them? At 20k I wouldn't think so. Look to see if your air filter is too oily, Assuming you have an after market air filter like Airaid or K&N.
 
#28 ·
ok i'll look into MAF cleaner. as for the plugs, i'm assuming what you assume..the only other owner was the original owner who had it from may 2013 when it was built to march 2014 when he traded it up and i got it in april. it had 6k miles on it, so i assume he didn't do anything. and my airfilter is the aFe Dry filter, and i opened it up and looked, and it looks fine. no oil in that bad boy since it's a dry filter.

I'm listening with poor computer spkrs....is it only 1x per shift? It didn't sound like engine knock to me but poor computer spkrs. Put out a call for someone local to listen mayhap someone in NJ can listen to it.
yup like right after the shifting you hear that knock that just sounds like two things knocking around in a can real quick and it stops.
 
#30 ·
I'm still wondering why he hasn't inspected the underside of the car, seeing as how the sound only happens when he is shifting... when everything would be sloshing around, and not at high load where pre-detonation would normally be occurring... rule the easy things out first...
 
#31 ·
I wonder if it's what many of us call the MT being notchy/drive shaft/suspension...consider coming up to CT for one of my cruises. You'll have a bunch of folks willing to listen and cars to compare it to. I know I'd like to hear/drive it and would be willing to let you try mine.

does it only happen at low rpm shifting? If so what rpm are you shifting at? consider raising it if you are getting out of 1-3 at less than 3k.
 
#32 ·
^^ The stock drivetrain is incredibly noisy, especially if you're clutching in while the car is still slightly under load. Lots of slop in the driveshaft, transmission, etc... I can get under the car and rotate our DS maybe 10-15* back and forth (standard transmission, in neutral) with just my hands.
 
#33 ·
I haven't gotten under the car bc its been ****ty and rainy out the past couple weeks so I'm not bothering. I can always get it to do it when you shift at real low rpms, like going into 3rd around 20. 3rd is the biggest culprit. sometimes it'll knock when you're continuously giving it gas, like in 2nd, around 2k rpm which is odd too. it stopped when I switched to v4 tune which sends the spark timing back to stock and seems to not do it as much on 93 octane... which again, is why I really feel this is engine knock. I'll have to get under it when the weather gets a tad better. maybe this weekend I'll put it up on ramps and see how far under it I can get, I'm a big guy lol. and I know how sloppy our drive train is because it constantly clunks when I shift so I know what the drive train noise is and this isn't it... unless this is a noise coming from the tranny itself, idk.
 
#34 ·
and Oxford, idk if it means anything but I remember when I first got the car I had that hidden check engine code.. like the light didn't light up, but when I plugged in my reader for the hell of it, I got something about crank position or something? and I remember reading online that if you did a couple of straight runs of 0 to 60 it'll go away when you clear it.. so i did it and cleared the code and it never came back. I can't remember exactly what it is, but it was crank something....
 
#35 · (Edited)
put some 92 in from wawa tonight as they were the only place open when i went to get gas, and i put the V1 tune back on. heard some knock still when i shifted crappy. drove about 30+ miles so the 92 is mixed in with the 89. i'll have to drive it all week and see if i still notice it. meh.

here's a question for you manual guys. when you're shifting normal and not getting on it, what rpms do you shift at?
 
#36 · (Edited)
2500, but our car has 3.55 and 27" tires. If you have the 2.73s, you're probably lugging the engine if you're shifting that low. With 2.73s i'd be shifting around 2700-3000. If i remember correctly, the car is well under 3000 rpms in 3rd at 50 mph, the 2.73 is just WAY too long of a gear.
 
#38 ·
hmm ok cool, thanks for the input. i'll have to see exactly where i'm shifting bc i know in my neighborhood and stuff where i hear the clank noise more frequently i shift a lot quicker since it's only 25mph
 
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