4.6 Timing Question

[DanielNodel]

So I recently had a pretty bad timing failure, I was driving one night and from about 60-80km/h I lost the ability to accelerate, foot to the floor and the RPMs did not rise what so ever, I let go off the gas pedal and the engine was just maintaining speed, didn't even slow down. After about 5 seconds, I guess the PCM noticed a power loss and downshifted my transmission about 2 gears and my RPMs shot up way too quickly to about 6k. I immediately headed home and even noticed a considerable power loss while driving. As I got home I got a CEL and got codes for bank 1 retardation, bank 2 advancement, cam position sensor codes, and even engine overspeed which I assume is from the instant acceleration from the PCM downshifting me. Everytime I reached about 3000-4000 RPM I noticed a rattling noise coming from the front of the engine, I instantly assumed my chain was slapping the timing cover so I took off my valve covers and found my tensioner guides broken to pieces, not chipped or anything, straight up 5 different pieces. Took off timing cover the same night and all 4 guides were smashed to bits. The tensioners were working, the chain was great and wasn't worn down as I did timing about 40,000 km ago, camphasers looked great but somehow my guides were destroyed. Considering I'm no where near the time frame for my guides to fail, what could have happened? I didn't replace the VCT solenoids but I cleaned them and I'm not sure how they could have contributed. Oil level and pressure are great and the tensioners did not fail, what am I missing here?

 

[94Eddie]

This is something that you might never know what caused the failure. It could be due to an installation error, part(s) failure, the harsh transmission downshift might be the root of the timing chain failure, etc. Did you use Motorcraft, or equivalent, parts? If I had to bet, I think the transmission downshift caused the guide failure or it was something that stressed the guides that were in the process of failing.

 

[DanielNodel]

This is something that you might never know what caused the failure. It could be due to an installation error, part(s) failure, the harsh transmission downshift might be the root of the timing chain failure, etc. Did you use Motorcraft, or equivalent, parts? If I had to bet, I think the transmission downshift caused the guide failure or it was something that stressed the guides that were in the process of failing.

What caused the inability to accelerate? I ended up getting new cam position sensors just in case, waiting on the guides to come in but maybe the PCM put the engine in some kind of limp mode while it was trying to figure out the positions on the cams then the overspeed broke the guides? I used a Cloyes timing kit which is generally a good brand, I've used their parts at least 20 times on 4.6s and 5.4s alike and tend to seem higher quality than OEM components in my opinion, I really don't think it was some kind of fault on the guides themselves.

 

[94Eddie]

What caused the inability to accelerate? I ended up getting new cam position sensors just in case, waiting on the guides to come in but maybe the PCM put the engine in some kind of limp mode while it was trying to figure out the positions on the cams then the overspeed broke the guides? I used a Cloyes timing kit which is generally a good brand, I've used their parts at least 20 times on 4.6s and 5.4s alike and tend to seem higher quality than OEM components in my opinion, I really don't think it was some kind of fault on the guides themselves.

My guess is that the PCM detected a problem and put the engine in limp mode which caused the lack of power. When this happens sometimes it will make overdrive unavailable which takes out 5th and 6th. This could be the reason for the two gear harsh downshift and the unresponsive accelerator pedal.

 

[DanielNodel]

My guess is that the PCM detected a problem and put the engine in limp mode which caused the lack of power. When this happens sometimes it will make overdrive unavailable which takes out 5th and 6th. This could be the reason for the two gear harsh downshift and the unresponsive accelerator pedal.

Seems very ridiculous that this kind of failure could be caused by just bad cam position sensors, Triton things I suppose

 

[94Eddie]

Seems very ridiculous that this kind of failure could be caused by just bad cam position sensors, Triton things I suppose

The 4.6L 3V doesn't suffer from the same problems of the 5.4L 3V. Overall they are very reliable if maintained properly as is the 6R80 transmissions. Events happened so fast in your situation that figuring out what was the root cause of the failure might not be possible. I think that one thing that is safe to say is that failure of the guides was catastrophic and fast. Whether the guides caused the transmission issue, or vise versa, probably will never be known. If you haven't done so, servicing the transmission would be a good idea, IMO.

 

[I bleed Ford Blue]

I used a Cloyes timing kit which is generally a good brand, I've used their parts at least 20 times on 4.6s and 5.4s alike and tend to seem higher quality than OEM components in my opinion, I really don't think it was some kind of fault on the guides themselves.

I've been watching a lot of YouTube vids on the 4.6 3v since I just acquired one. When it comes to timing chains, guides, and cam phasers, all the top techs recommend original OEM ford parts. The other brands like Dorman, Cloys, and the various no name Chinese brands may look better than the ford stuff, but they don't hold up as long as the ford stuff does. When I redo mine its getting all new genuine ford parts.

 

[DanielNodel]

The 4.6L 3V doesn't suffer from the same problems of the 5.4L 3V. Overall they are very reliable if maintained properly as is the 6R80 transmissions. Events happened so fast in your situation that figuring out what was the root cause of the failure might not be possible. I think that one thing that is safe to say is that failure of the guides was catastrophic and fast. Whether the guides caused the transmission issue, or vise versa, probably will never be known. If you haven't done so, servicing the transmission would be a good idea, IMO.

Transmission fluid and filter were changed very recently, also doesn't shift harsh or clunk at all in normal driving conditions. If I'm not mistaken the timing on the 4.6 and 5.4 are pretty much identical? From what I've been told though I've never really seen it in person, the solenoids get stuck open and the camphasers get constant oil pressure and go haywire, pretty much just explode into pieces, which causes the timing issues. Or bad oil pressure from faulty pump or bad/old oil and the solenoids and phasers dont function properly causing its own issues. But yeah I have no idea what happened, I can only imagine the cam position sensors caused the limp mode, which caused harsh downshift, which broke guides but i guess at this point doesnt change anything. Youd think that the PCM wouldnt downshift you 2 gears for any reason but oh well. Maybe some kind of function to lock your phasers at speed instead of only at idle to prevent these kinds of failures would have been great. The whole no overdrive thing while in limp mode has to be an oversight, especially if youre in 6th in that moment, doesnt slow you down either or anything just money shifts in an auto lol

 

[94Eddie]

There are some differences in the timing components between the 3V 5.4L and 4.6L engines. There is a clear difference in the far fewer failures of the 4.6L as compared to the 5.4L engines. There were a lot of the 4.6L 3Vs put in F150s, Mustangs, Explorers and Mountaineers. I have been a member here since 2003 and have read about very, very few 4.6L 3V catastrophic failures of any variety. They are also relatively few catastrophic failures of them in the 2005-2010 Mustangs even with them being beaten hard. As for the downshifting, it probably is hard to anticipate every scenario of failure and mitigate for it in software controls.