Help! New Engine Noise

1997ThunderbirdLXV6

1997ThunderbirdLXV6

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Got into my car. Opened windows. Started engine; startup was normal. I immediately noticed an unknown noise. Opened hood and recorded video below. What is this???
  • Appears to originate from top center/center right of engine.
  • Sounds like a very fast tick (?).
  • After recording, I shut the engine off; I did not check as of yet whether it changes with rpm, with shifting into gear, with A/C on, or whatever other condition one could come up with.
  • I gave it a tiny bit of throttle, but all I can say is that the sound persisted.

 
Bring up the RPM a few thousand and see if follows the engine speed. That will help narrow down if it is in valvetrain. I'd assume not, usually they are more of a heavy sounding metallic knock. Seems like more of a tick of a solenoid or sensor.

Also, you can take off the belt and start the car for a moment, that will eliminate the belt driven accessories.
 
I'm not too familiar with the 3.8s. The 4.6's often can get a ticking noise in the back from the EGR tube nut being lose.
Could be an exhaust leak
 
Ok...this is weird.

I just went back out to my car, armed with gloves, a tiny hammer, and protective eye wear. Get in, start the car, and...

Yeah, noise is gone. Wtf?
 
If you get a long screwdriver, you can use it as a stethoscope, put the blade on a part and put the handle up to your ear, that should help narrow down where it is coming from. My first thoughts are possibly the IAC, but it seems to fast for that. It could possibly be a loud fuel injector. It could also be an exhaust noise like was mentioned, since the EGR tube is right there.

I just read that the noise went away. This leads me towards an exhaust noise. Sometimes cold exhaust can make weird creaking type noises as it heats up.
 
Like Mike said exhaust leaks can go away once the engine warms up. When the EGR tube was lose on my Cougar it did just that. It had a tick until the engine warmed up for a few mins.
The fix was just tightening the tube nut. Hopefully it's something simple for you as well!
 
MadMikeyL said:
. My first thoughts are possibly the IAC, but it seems to fast for that..
Click to expand...

That was my thought, too, because this IAC has a history of malfunctioning. It once left me totally stranded in a supermarket parking lot, unable to keep the engine running without throttle pedal. Ultimately, taking the IAC off and cleaning and shaking it resolved that issue.
In this case, if IAC related, I would expect a more irregular idle. The idle was a tiny bit shaky, but not dramatically so.

MadMikeyL said:
I just read that the noise went away. This leads me towards an exhaust noise. Sometimes cold exhaust can make weird creaking type noises as it heats up.
Click to expand...

I hear you...
But it really sounded sort of electromagnetic/solenoid-ish to me. Could be a combination of both if EGR related (?).

The other thing that sounded similar was when I had that coilpack issue a while back. Those flashes sounded the same, but they were visible and combined with noticeable misfire.
Just a thought: what would a loose spark plug sound like?

Kenz said:
Like Mike said exhaust leaks can go away once the engine warms up.
Click to expand...

The car won't fully cool down until tomorrow; it's a warm day. I'll see then if the noise returns.

I'm not entirely in favor of that theory though. The first time I ran the engine, with the noise, it was running for several minutes. The exhaust would heat up pretty quickly; if heat related, I think the noise would have (gradually) gone away then already.
 
I'd guess IAC chatter.

Not to say ignore it but it doesn't sound serious. Hey my 96 3.8 spun a bearing with no warning, and the 04 5.4 went 3 years with a bad rod bearing (lets not talk about that one).

Suggest clean the IAC and EGR.
 
The IAC is a stepper motor, not a solenoid. It could still be the culprit, especially if there is play in it and the airflow through it was just right to cause it to rattle. The EGR itself is vacuum controlled, but the vacuum solenoid is that round black piece to the left of your hand when you were touching the IAC. But EGR should not be commanded at idle, and if it was, you would have a very rough idle. The fact that it sounds like a solenoid is what let me to think an injector. Also the frequency of the noise sounds close to how fast the injector would be cycling.
 
MadMikeyL said:
The fact that it sounds like a solenoid is what let me to think an injector.
Click to expand...

But why would an injector do this? And wouldn't that cause some sort of rough idle, too?
When I gave it that little bit of throttle (maybe idle + 600 rpm), I think the frequency didn't change. I was scared to give it any more revs because I had no idea what I was dealing with.

My idea of a loose spark plug doesn't sound plausible?
 
It is easy enough to grab a socket and ratchet and check them, but that doesn't sound like a loose plug to me. To my ear it sounds like a fluttering PCV valve, but it is hard to tell sounds from a recording. Your best bet the next time it comes back is to grab a long screwdriver as mentioned above and listen to different components while it is making the sound.
 
It could be a loose plug, but unless you just did plugs, they don’t tend to loosen on their own. Also the plugs are down lower and on the outer sides of the engine. Where you were zoning in on the noise is nowhere near the spark plugs. It’s easy enough to check though. If it is going to be something loose causing a ticking like that, I would be more suspect of something exhaust related. An injector can be loud without necessarily affecting fuel flow. The PCV theory is possible too, and those things are cheap enough, might just want to replace it as a maintenance item.
 
To me that sounds nothing like an exhaust leak ... more like either electrical arcing or a noisy motor or slipping plastic gears. At that RPM the injectors or plugs wouldn't be firing that fast, and the sound is too "Fast, slow, fast, slow, pause, slow, fast" etc. to be tied to RPM. Unless it was the coil pack itself doing that... but you said it sounds like it's coming from the back, not the front.

I'm going to go out on a limb and suggest possibly the IAC making that noise... I also like the previous idea of a fluttering PCV valve; I could see that kind of noise from that.
 
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