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Austin Travis 08-08-2019 06:29 PM

Causes of valve chatter.
I have a 2004 3.9l v6 Mustang with 125k miles and the valves started chattering with 87 octane a few months ago so I just started running 93 octane and now they’re starting to chatter with 93 octane. The chattering doesn’t appear until driving for after about 30 minutes. The chattering starts with a very light load on the engine and then disappears after about 3500 rpm. It is the loudest when accelerating around 2500 rpms and at highway speeds with even the lightest touch to the throttle. I have new spark plugs, no slack in timing chain, there are no exhaust leaks, good egr, and the imrc actuator rods are connected. Does anyone know what could be the cause of the valves chattering? And would torquing the rockers possibly have any effect? Thanks.

wmburns 08-08-2019 09:00 PM

Just so I understand. Switching to 93 Octane quieted the noise down for a period of time?

IF this is true this tells me the problem is carbon build up. If true this means the noise is more likely to be pinging.

This creates a cause an effect situation. Some typical cause of carbon build are:
  • Weak ignition
  • Excessive fuel
  • fouled spark plugs
  • compression problems (too high or too low)

How about trying some CRC intake cleaner to start?

Another way to find out is to perform a compression test. If you find that the compression is actually too high, this is another sign of carbon building up raising the CR.

In the interest of being through it might be a good idea to confirm good oil pressure.

Austin Travis 08-09-2019 09:26 AM

Yes it did completely quiet it down at first but after a few thousand miles and it eventually started to ping again. I have good oil pressure and I know I have leaking valve seals on two cylinder but I don’t know if that could be the cause of the buildup or not. I have a borescope ordered and I’m gonna look in it tomorrow when it arrives.

Travis98146 08-09-2019 04:38 PM

It sounds like you may have ignition ping rather than valve chatter. If you have low oil pressure, lifters/rockers may chatter when you get warmed up or with a change in throttle position/rpm.

wmburns 08-10-2019 12:12 PM

+1 on above. I also agree it's ignition "ping" related.

Consider that one possible carbon source could be the leaking valve seals.

+1 on using a borescope to see inside the combustion chamber.

tangalang 08-11-2019 12:33 PM

I'd check the upper intake manifold runner control. It's all the way up against the fire wall.look to see if one of the two arms are off.

Austin Travis 08-11-2019 10:58 PM

1 Attachment(s)
Attachment 611083 this is how cylinders 2 and 4 looked but all of the others had very little carbon, would this be enough to cause a ping?

tangalang 08-21-2019 11:08 PM

Any updates? I had a very similar issue with my 2003 v6, it was a fix with the intake manifold runner control,two bad clips that didn't open up with no codes.

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