Inconsistent Car Tapping/Rattling After Header Install


New Member
Sep 29, 2021

I'm working on a manual 2004 Mustang GT 5 speed that's been making an awful tapping/rattling noise. It is very loud(hard to have a conversation close to the car while running) and is inconsistent. It seems to speed up with the engine, but the sound is off beat from the rhythm of the engine. As the car gets up to operating temps it gets much more consistent and seems more in rhythm with the engine. The sound goes away when the engine is under load, especially higher gears and overdrive. But seems to get louder while decelerating and changing gears. It completely goes away if the car is in too high of a gear.

Using a breaker bar as a stethoscope, I found that the sound is coming from the driver side head, towards the very front(I believe it's were the timing chain is?)

I just replaced my exhaust manifolds with shorty headers and I'm running an oxygen sensor code: P0161

also, the car stalls when making turns with low RPMs(mostly when parking), and if the AC is turned on.

I have three videos of the sound. The first one the engine is not at operating temp. The second video the engine is at operating temp. The Third video the engine is at operating temp and I used a breaker bar as a stethoscope and put the microphone against it to help bring out the sound. I also have a picture that shows where I believe the sound is coming from.

Not at operating temp:


operating temp:


operating temp through stethoscope:


Sound location:

Tapping Location.jpg

I've found threads with similar problems, but every case of tapping/rattling/knocking seems to be different so I wanted to get an opinion specific to my car before I go tearing into it. I appreciate any help I can get with this. I am also happy to provide more pictures or videos if needed.

Thank you!
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That's what I was thinking, although I wanted a second opinion before pulling off the cover. Is there anything I should be looking for specifically? or will it be obvious what's at fault?

Also I'm assuming then that my stalling issue is due to something else. The same thing was happening a year ago and a shop replaced the IAC for me and it fixed the problem. How would I check if the IAC is at fault?

So I took off the timing cover and found a lot of slack on the driver side timing chain. My guides were completely worn down to the metal and the driver side tensioner was sticky. I bought a Cloyes timing kit from summit racing and replaced the chains, guides, and tensioners.

Cloyes timing kit -->

Unfortunately, there is still a ticking sound, although the sound is not nearly as loud. I pulled the valve covers off and checked the lash adjusters and found at least half of them are worn down(I can easily compress them with my finger, some of them completely). I ordered some new ones which will be coming in Friday. Hopefully that is what's causing the problem, I will know when I replace them next week.