@jav1 thank you for your thoughtful, very well organized and expressed debate. The Ford Ti VCT Valve Timing video is very good for conveying the concept of hydrolic VVT Phasers. Admittedly - I know nothing about the Coyote Ti-VCT, ie: if its solenoid design is any different from the 5.4L like that in the FordTechMakuloco video. But I do believe the 'pressure port' on the VCT Solenoid at issue is the middle one of the three side ports on the shaft - NOT the end of the solenoid where the spring is located. I believe THAT is the exhaust port. I do not have a ton of good documentary support for that opinion other than the attached "ENGINE OIL SYSTEM" section from my Ford Factory Service Manual. Magnifying it doesn't seem to resolve the question with any degree of certainty.

However, having removed solenoids and peered down into the rather vast hole, and having dissembled the Solenoid Valve Bodies and cleaned all the ports (admittedly for reasons other than determining this issue), I firmly believe the spring end of the solenoid is the 'forth' or 'exhaust' port you refer to in paragraph 2 rather than the 'pressure' port. Other than that issue - I summarily agree absolutely 100% with your understanding of the system as expressed in paragraph 1 and in paragraph 2. In any event I believe we can both agree, whatever the design of passages be - the solenoid's electro-magnetic movement must be independent (and unaffected) by inlet, or outlet, oil pressures. The fluctuating oil pressure imposed by engine RPM - as well as commanded solenoid duty cycle should be _spool 'position' independent_ and exert identical upward / downward force on the 'spool' at all times. In this manner, the duty cycle induced magnetic field can very preciously modulate the spool position against the spring's force - directing all available oil pressure (whether 15 lbs at idle, or 60 lbs at road speed) into the proper phaser chambers (either advance or retard). Ground side Duty cycle modulation of a constant voltage source if by far the preferred technique of precious control.


I can attest from extensive monitoring of the VVT system (as shown in post 3036 above), the duty cycle reading runs VERY steady when any degree of retard is desired. This differs from your description in practice, but not conceptually. The duty cycle is ZERO when NO retard is requested. However, if 10% retard is requested by the PCM, duty cycle jumps way up (50-60%) and bobbles briefly settling down at 'equilibrium' in retard/advance chambers, and STAYS there unless the PCM increases or decreases it -very slightly- to increase or decrease cam position. But basically, when active, duty cycle doesn't vary up or down even 1% for a second or so to 'reposition' cams, - then it returns to about 44.5% or 44.6%, achieving equalized pressure in both advance / retard chambers holding the Phaser - RIGHT THERE - at desired retard (dictated by RCAM)! I do notice much bigger spikes but lower 'RMS' duty cycle % with thicker oil, or on cold startup. (that sorta' makes sense to me - the thicker oil is lazyier).


In paragraph 3 you ask - "BUT- is there any reason to believe that this PID wouldn't still log in open loop?" YES. The reason is the above referenced extensive monitoring of the relevant OBDII signals. Without that, the logic programmed into the PCM would be anybody's guess. Outside of that, I agree, there would be no reason the PCM could NOT continue to indicate an Error factor from ZERO. But I have observed, and witnessed, - when the PCM determines it is having difficulty maintaining cam position within its acceptable limits (IDK exactly what), the PCM WILL DEFINATELY 'shut down' vVT system. VCTENA signal goes false. The scanner's response to RCAM query return an absolute ZERO. Duty cycle to both solenoids goes to absolute ZERO, and both cam error is absolute ZERO. (Now, admittedly - this observation could be flawed respecting your question in a case of severely low oil pressure OR if MY vehicle was actually returning the cams to default position and the locking pin was locking them at ZERO - which it SHOULD DO). In this regard, I do notice in the FordTechMakuloco video, he mentions 'changing the OIL pump'. (which required removing the front cover -- all over weak springs in the VCT solenoids and without changing phasers/chains? IDK?).


But, if an OBDII response to a scanner query is ZERO to each query, I do not understand the 'giggling' signal being exhibited on the video's IDS system.

 

F150-

Thanks for the thoughtful response! I really enjoy trying to understand the technical side of how /why things work or don't as opposed to just swapping parts to fix something.

I think I understand most of what you posted but i'm a bit confused by somethings and, you have some very interesting data on duty cycle that I like to expand on.

My understanding of the VVT system (which may be wrong) was that it was disabled during warm up... which is why many of these problems don't manifest the worst symptoms until the engine is warm. So I would ask :

I'm parsing a few sections of what you wrote to illustrate where I'm getting confused: You mentioned that -- "duty cycle is zero when no retard is requested... but when 10% (I presume you meant degrees?) retard is requested, duty cycle jumps to 50-60%....then it returns to about 44.5% or 44.6%, achieving equalized pressure in both advance / retard chambers holding the Phaser - RIGHT THERE"

That confuses me because in my mind there should be 3 main solenoid functions. 1) hold cam steady 2) advance cam 3) retard cam. NOW- I understand the advance and retard (and hold) functions can be modulated for quick or slow corrections and they should work in a "range" of duty cycles. I'd even understand a relatively stable duty cycle if the system response is excellent but what I don't get is how both 0% duty cycle AND 44.5%-44.6% can both produce the hold (equilibrium) function"??? Especially if 50-60% elicits a retarding function?

I guess it would make more sense to me if something like 0-35% was advance- 36-66% was hold and 67-100% was retard.... or some other logical set of numbers corresponding to the 3 functions?? ( Such as 0-10%= hold - 11-60%= retard - 61-100% = advance).

Is it that until the engine is warm and the VVT system is disabled, the VVT system is set such that 0% duty cycle is defaulted to full advance?

 

Likewise for me, understanding technical stuff can sometimes become an obsession! Such was the case with the Phasers / VVT system when my 'O4 developed P0022 problems around 200K mi. I found in deapth information scant and difficult to acquire. One key reason, a surprisingly wide range of variations in veh. mfg's OBDII parameter assignments and PCM functionality - even among similar models. Therefore, much of what I have to offer relates heavily to the Triton - 2004 through (probably) 2010. For 'fake news' inoculation (full disclosure), outside of those models - certain opinions expressed here might perhaps be suspect - but never intended.



Your response indicates you correctly intrepreted/understood all I wrote - but hold one faulty understanding (at least as to the subject models).


That is incorrect. Even before my timing job - on (cold or hot) startup the PCM would set VCTENA true within 3-5 seconds. Bare in mind, mine ran fairly OK, just startup chain rattle, _when warm_ rough idle, diesel knock, lifter tick, and I could predictably produce a P0022 DTC by fluxuating accel rapidly. Also, after (30-ish) miles, VCTENA would go false, seemingly for no reason and - NO MORe VVT for the remainder of THAT drive cycle. But if I shut key off and immediately restarted - VCTENA would come true again for another random, but shorter distance. Post timing job - VCTENA still pops right on (3-5 sec). Though there is NEVER requested retard at idle (or anytime below ~ 800 RPM, or 25% engine load regardless of speed/RPM). Under THOSE conditions there is '_Zero_' duty cycle pulses applied to either solenoid and the cams should remain at base (NO-Retard) or ZERO degrees - but by virtue of Phaser spring loaded locking pin, not necessarily oil pressure even though 100% of available oil flow/pressure is routed to the advance chambers by the inactive VCT solenoid.


I believe your perception of the phaser's hydrolic operation may be slightly burdened by rose colored glasses of a 'Perfect World". In a perfect, sealed chamber, phaser (OR where the spool valve could be COMMANDED in both directions as with an excavator arm), once proper cam positioning was achieved - you could shut off all duty cycle modulation and oil flow into/out of the Phaser chambers would remain unchanged (theoritically stay right there). But as soon as solenoid duty cycle(s) cease, the spring pushes the spool valve up - routing 100% of available oil pressure ([< 25 at idle/coast >45-70 at HIGH RPM]) into the advance (OR NO RETARD) chambers advancing the cams toward 'maximum' advance direction. NOTE: I mention 'available' OIL PRESSURE and 'toward' - because it an important factor that relates here. But that aspect is discussed extensively in another post: https://www.f150forum.com/f4/final-r...7/#post4436341


For discussions sake here, I'll just say applying 'nominal' oil pressure into the advance chambers allows (a properly operating) phaser locking pin to capture the phaser at ZERO degrees and the locking pin is what holds it there at ZERO - NOT ZERO DUTY CYCLES. If oil pressure is higher (>25 lbs) due to higher RPMs, the higher oil pressure overcomes the locking pin spring and disengages it. If there is STILL no duty cycle pulses being introduced to the solenoid - ALL available oil pressure is still being routed to the advance chamber and advances the cam 'a slight bit more' to the full extent of the advance chamber (some slight amount, perhaps 3º to 4º true ADVANCE, but beyond the locking pin). See PHOTO & more description in the linked post.


When RETARD is desired, just enough duty cycle need be applied for the spool valve to overcome the spring - JUST ENOUGH to tip the scale of oil pressure between advance/retard chambers in favor of retard momentarily (enough overcome the force necessary to move the phaser vanes + overcome oil seepage, + push oil out of the advance chambers back out the solenoid and out the exhaust port). When cam positon matchs RCAM (there is typically some 'overshoot', the duty cycles can be relaxed (lengthened) just enough (VVT Closed Loop) to hold the spool valve against its return spring at that position, maintaining equal oil pressures between advance/retard chambers - AT WHATEVER physical retard position the cams are in at that moment. In my vehicle's case - that percentage duty cycle is around 40% cold, and 44.5% hot.


I believe THIS parameter is VERY TELLING in VVT System health. A very HIGH % woud indicate low oil pressure, or leakage difficult to supply/overcome. A large descrepancy between Bank1 & Bank2 duty cycle would indicate lower/higher oil pressure in one head (compromised tensioner seal), or unbalanced cam bearing friction between 1 & 2 (bad cam bearing), or oil passageway obstruction. But my live readings (post 3036 above) are within .1 % and hover near 50% - which gives the PCM maximum adjustment in both directions to achieve desired cam positioning (Healthy). Of course Cam Error tells whether the PCM _thinks_ everything is working or not.


Pictures are worth a 1000 words. Graphs are worth a Million: The First graph on cold startup. Org trace=CAMERR1, PINK=CAMERR2, Green dotstring=VCTENA, Red=solenoid1, Yellow=solenoid2, Blue= PCM's Requested Retard in CKSº, White=Engine Load.


Note changes in RCAM corresponds with an immediate Spike in ERROR "+" or "-" (over advanced / over retarded) cam position error. But when solenoid duty cycle reacts, the cam settles down - solenoid duty cycle then Level out around 45% no matter where the blue line (RCAM) is at that moment - so long it is not at zero.






V.V.T. operation on startup out of my neighborhood 25 / 30 mph - start stop.




Note below that RCAM going to ZERO, or Engine Load (white dashed trace) exceeding about 75% sends solenoid duty cycle to ZERO - to put cams at ZERO RETARD or FULL advanced position - depending on amount of oil pressure available at that time.



Graphs are produced with Torque Pro - through the Plug-In "Realtime Charts for Torque Pro" from Google Play ($1.99). I rate both applications 5 Star.


It is my hope this information helps many who struggle with cam / phaser difficulties that I believe are frequently mis-diagnosed.

 

AWESOME post!.. I need to read it several times to grasp it all but I get where My confusion was originating (cam zero (lock pin location)- versus zero duty cycle which is in essence EITHER full advance (3-4 degrees advance past cam zero without the lock pin engaged) OR cam zero when oil pressure allows the lock pin to drop.

GREAT INFO!!

 

Damn - you have successfully and accurately consolidated everything I said into one very short paragraph.


Took me so long to reach my beliefs about it, guess I did not expect anyone to grasp it so quickly.

 

Thanks but your not alone!! I've been trying to understand exactly how this system is "supposed" to work for a while. Evaluating the many failure modes isn't easy. I also believe there's frequent misdiagnosis and parts are thrown at "perceived" problems when the parts replaced are just the symptoms of the "real" problem.

I need to go read your other link but I've often surmised their maybe some other factors (that I think you elude to) related to hydraulic response times and how they may change as an engine and/or components wear.

I'm sure the PCM and programming did take into account "some" of those factors but I doubt they captured them all. IE. Did the programmer account for things such as tensoiner seal failures? Or the additional torque required to adjust a phaser when 1) oil pressure is sub optimal or 2) the torque required is greater than expected because of bad cam followers/lash adjusters or 3) - even just the speed/latency at which the phasers react because of various combinations of these problems?

I still don't get it all but everyday I learn a little more... thanks to guys like you who log everything and don't just Betty Crocker ..."replace xyz component and hope for the best".

 

Thank you! I just bought this truck and its having this issue! Glad I saw this post. You saved me from buying the new engine! Exactly the first thing the mechanic went to. Any updates I'd love to hear!

 

Exactly what many many "so called" mechanics say. I'd like to know how many owners @s_vares has saved from buying new engines by starting this thread.


What model truck did you buy, and what symptoms are you seeing?




BTW. Welcome to the forum.

 

This is a great posting. So my engine light is on and can not be reset. So my 2006 F150 with 126k miles can no longer be inspected unless I do this repair. Of course like most of us I dont have $2500-$3000 sitting around to fix it. Im considering a DIY since the truck has been sitting for 6 months. I see the Ford parts are about $550 where others can be as low as $200.

The videos are great as well as the pictures.

Im still trying to get a shop manual. I see tons of downloads but they all seem to want to sign up for crap.

A question I havent seen the answer to. Do I need to remove the new sparkplugs I installed last year?

Would a better oil possibly let me skip the cam phaser repair?

Anyone in Raleigh, NC that knows more?

 

See this thread for the manual: https://www.f150forum.com/f4/free-20...manual-298753/

By removing the spark plugs, it would make the engine easier to turn over but you should have to remove them. If you do, you should be able to re-use them.

At this point, I believe you need to do the phaser repair because the damage is already done. Better oil may or may not prolong the time the phasers need to be replaced.