Modded Mustang Forums banner
Cancel
Create thread New Garage Forums

knocking under idle

Jump to Latest
1 - 19 of 19 Posts

watson

· IG: opiesvt
Joined
·
8,783 Posts
Discussion starter · #1 ·
Alright, I did a search and while it brought up a few related topics, they weren't exactly what mine sounds like.

I have this knocking noise during idle...it can be either on a cold start or warmed up. I don't hear it when I'm driving (can't hear **** because of the full exhaust). Here's a quick video


Like I said, a lot of people say it happens while driving, only on cold startup, only when the engine finally gets warmed up, while going over speedbumps, only when clutch out...so many variations

Mine does it just sitting there idling. Immediately following the knock, the RPM goes up by about 200, then goes back down. It does that every time it knocks. And it's not constant, perfectly timed out..it's sometimes once every 10 seconds, once every 20 seconds, or in groups like the video portrays.
 
#3 ·
You are talking about the sound that happens every few seconds, not the sound that is constant? The constant ticking is just injectors. The tap, or knock that happens every few seconds is strange. It doesn't seem like it happens at regular intervals. I have no idea.

I doubt its dangerous though... If it were a worn rotational part, you would hear the tapping constantly.
 
#4 ·
Are you 100% sure the noise is coming from the engine? Any loss of power? It couldn't be a flap in your vents could it? My dad's F-250 has an annoyingly loud thud sound coming from under/behind the dash
 
Save
Reply Quote Like Like
Discussion starter · #5 ·
It's definitely coming from the engine. The CAI kinda amplifies it.

And no, I'm not talking about the ticking..it's the knocking noise. It's not constant/perfectly timed out like you said about it being a rotational part.. I'm thinking maybe a valve.

No loss of power. It doesn't get louder under heavy throttle.
 
#6 ·
Hmmmm....you need to isolate the sound source. CAREFULLY. Go buy a mechanics stethoscope.

Wear short sleeves so your sleeves don't get sucked into the FEAD belt, and be very careful.

Listen at the cam covers...near each plug...look for something loose near the FEAD belt routing - down near the power steering pump. Check the coolant hoses and belt relationship. If you isolate it to being under a cam cover, pull the cam cover and investigate. VCT possibly?

Have you checked your plugs lately? Inspect all your COP's as well.
 
Save
Reply Quote Like Like
#7 ·
try pulling you air filter off and dont drive it just let it idle.could your filter have somehow broken down or have a tear makeing that noise? deff. does not seem ratational which is really good.
 
#8 ·
DiMora said:
Hmmmm....you need to isolate the sound source. CAREFULLY. Go buy a mechanics stethoscope.

Wear short sleeves so your sleeves don't get sucked into the FEAD belt, and be very careful.

Listen at the cam covers...near each plug...look for something loose near the FEAD belt routing - down near the power steering pump. Check the coolant hoses and belt relationship. If you isolate it to being under a cam cover, pull the cam cover and investigate. VCT possibly?

Have you checked your plugs lately? Inspect all your COP's as well.
Click to expand...
This^^. I had never even seen a mec. Stethoscope until DiMora showed me one and i used it. They are pretty freaking amazing.
 
#9 ·
I kind of have the same knock, it's my through out bearing "TOB". It's hard to tell by your video.
 
Save
Reply Quote Like Like
#10 ·
And find out if it does it when your or at idle speed. Have someone give it som gas while your under the hood listening. I swear I'm gonna put together something to send a signal to the throttle when I'm under the hood. Anyways it kinda sounds like something external but it is hard to tell from my phone speakers. Check your header clearances and what not. It's a pretty wierd noise.
 
Save
Reply Quote Like Like
Discussion starter · #11 ·
DiMora said:
Hmmmm....you need to isolate the sound source. CAREFULLY. Go buy a mechanics stethoscope.

Wear short sleeves so your sleeves don't get sucked into the FEAD belt, and be very careful.

Listen at the cam covers...near each plug...look for something loose near the FEAD belt routing - down near the power steering pump. Check the coolant hoses and belt relationship. If you isolate it to being under a cam cover, pull the cam cover and investigate. VCT possibly?

Have you checked your plugs lately? Inspect all your COP's as well.
Click to expand...
stri8ed said:
This^^. I had never even seen a mec. Stethoscope until DiMora showed me one and i used it. They are pretty freaking amazing.
Click to expand...
I used something similar when figuring out which pulley was making noise. Turned out to be the idle tensioner puller. Used an old piece of driftwood from my old terrarium..put one end of it on the puller and put my ear on the other end lol. Worked great.

And yea, I'm pretty sure it's coming from under the cam* cover. I mainly wanted to know before it goes into the dealership tomorrow...I bought an extended warranty from my bank and don't want to get in trouble for running a tune on it (I could bring it back to stock but then it'd idle funny). Also, they could say that the problem is a direct result from that, the CAI, or the TB, voiding my warranty.
 
#12 ·
LethalDosage said:
I used something similar when figuring out which pulley was making noise. Turned out to be the idle tensioner puller. Used an old piece of driftwood from my old terrarium..put one end of it on the puller and put my ear on the other end lol. Worked great.

And yea, I'm pretty sure it's coming from under the cam* cover. I mainly wanted to know before it goes into the dealership tomorrow...I bought an extended warranty from my bank and don't want to get in trouble for running a tune on it (I could bring it back to stock but then it'd idle funny). Also, they could say that the problem is a direct result from that, the CAI, or the TB, voiding my warranty.
Click to expand...
If you think it's coming from under the cover why don't you pull it off yourself first and see if there is something obvious? I think if there is something banging around in there you will be able to spot it pretty easily.

I was thinking a little more about this and since it effects your idle when you hear it and you think it's coming from under your cam cover, it could well be your phasers or maybe even your chain tenioners. The timing chain might make that kind of a noise if it is slapping around in there and your cam timing would change up a bit when it did this too. IDK, just reaching for **** here to give you some ideas.
 
Save
Reply Quote Like Like
Discussion starter · #13 ·
Any other time, I would pull the cover off n check out what's going on in there. I do my own work most of the time. Only problem is we have bad weather comin in right now so that's a no-go.

Thanks for all the help, guys. I appreciate it.
 
Discussion starter · #14 ·
So I just got a call back from the dealership.. they said the problem is with the throttle body.

So, for future reference, everyone who's having the same issue should check that first ;)
 
#15 ·
Wow, your TB was making that noise. What exactly was wrong with it? The butterfly snapping shut? I can't imagine it making that kind of racket.
 
Save
Reply Quote Like Like
Discussion starter · #16 ·
They didn't say...kind of sounded like they were in a hurry to get off the phone. I'll ask them what exactly they thought it was but yea, I don't know what would cause it to knock like that...
 
#17 ·
I dropped spark and fuel to each cylinder to see if a similar noise went away. It did on cylinder one on mine. Had someone look at it and they said it was a rod bearing.

You can just unplug the harness going to either the COP or injector.
 
#18 ·
That is an odd issue for a TB to cause. If it happens again, and I fear it might because that sounds so off the wall, try disengaging the clutch and see it if subsides. There is a "knocking" sound that goes with too much throw out bearing play. I have experienced this on both my s197s as well as having a friend who has the same on his


Sent from my iPhone using AutoGuide.com Free App
 
Discussion starter · #19 ·
That's what I was thinking.. when they told me it was the TB, I didn't quite understand how it could be making that noise.

The weather is finally clearing up here so this weekend I'm gonna tear it down. reps to both of you
 
1 - 19 of 19 Posts
About this Discussion
18 Replies
10 Participants
Last post:
watson
Modded Mustang Forums
posts
6.3M
members
83K
Since
2005
A forum community dedicated to all Ford Mustang owners and enthusiasts. Come join the discussion about performance, racing, builds, modifications, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
96 - 04 Modular Mustangs 5.0 Mustangs New Members Introductions Classic Mustangs