I have a 2000 4.6L and am experiencing what sounds like a detonation/popping/run-on sound in the engine when RPM's are returning to idle but the engine does not sound like it is going to stall. It occurs for 3-5 seconds and occurs whether the engine is hot or cold. I have also noticed the following:
- Occurs more frequently in humid weather
- Higher octane fuel minimizes the noise a bit
- lots of black soot on outside of tailpipe
- drivers following notice black smoke coming from tailpipe when de-accelerating
- occurance is shorter (3 secs) when engine is cold and longer (5+ secs) when engine is hot.
- does not "feel" to have near as much power/torque/get up & go as my previous 1998 4.6L Auto SC, STX.

I have taken it to the dealership (10,000 kms service) and they didn't hear the noise. They ran some engine diagnostics and everything checked out OK. I now have almost 15,000 kms on it and it is getting louder and more frequent. I have a the noise recorded on a small handheld personal recorder but the wind noise is so loud you can hardly hear the detonation sound (sounds like popping on the tape. The noise is louder when recorded at the back of the engine compartment then the front and is loudest on the drivers side vs the passenger side.
Last night I crawled underneath the truck to take a look and noticed soot on my tailpipe right where it exits the muffler. When I looked at the back of the muffler there is a small (about the size of our key tips) hole below where the tailpipe has been welded to the muffler (welding burn-thru??). I never noticed this hole before and am wondering this hole might be causing the problem if it has been there all this time?? Would a hole that small cause enough of a drop in back-pressure to cause engine problems?

Has anyone else experienced this problem?
Any suggestions on what it could be??

Thanks all,
Wayne

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2000 Lariat SuperCab 2WD Flareside 4.6L 3.55LS, Class III Tow, Black/graphite int, Rear Slider, Keyless Entry, Captains Chairs, Fibertech Hard Tonneau, Ford Cab Bars/Steps, Tinted Windows. Pretty stock right now!
2000 Mustang Convertible, V6, Auto, Triple Black, leather, MACH 460 stereo, 16" Alum wheel/tire package, included the very small back seat hence the F150 is now the "family" vehicle.
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The hole in the muffler ( back end of muffler ) is normal, it is a water drain, when emission system is operating properly it converts the harmful ehuast gasses into water vapour, you have probably seen vehicles on the road when they go around the corner water runs out of the tail pipe? As for the black soot in your ehuast and the puff of black smoke, i would suspect an over fueling condition, request that your dealership monitors the maf sensor and perform a relative injector flow and the such, wds can easily do this ( fords new scan tool ) or they can use the sbds, if the check engine light is not on now it should come on in the near future as the o2s will be reading rich, the wds also shows pending dtc's. This is just info for you as the concern will have to be duplicated at the shop, but this is a good start.

 

a little for info for you, an igition miss can also cause an over fueling codtion as incomplete combustion has taken place

 

Shhhhhhhh! Don't tell anybody, You've got the PSDiesel!

 

I have heard the same thing, I have a 2001 Screw 4.6l. I only heard it once, but I'll pay more attention and let you know if I find anything out.

Rick