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Old 06-12-2018, 02:52 PM   #1
hunterhicks
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Default Need a good 4.6 DOHC diagnostics/whisperer

Howdy all, running out of options (and life force) for a poor running 4.6 dohc motor after a timing set replacement. I seemed to have caused a secondary problem- car ran fine (minus noise) before replacement. After replacement, it has a rough idle and power loss.

I need someone that is good at diagnostics (and has a full Ford IDS scanner) to just tell me what the problem is- do we know someone on the level of scannerdanner or FordTechMakuloco (youtube). Need an answer, I’ll take care of the work.

Thanks everyone-

For those interested:

2005 Aviator 4.6 aluminum dohc 4v is the patient. Similar motor to the Mach 1, and earlier cobras. The last version of this motor as far as I know.
I have been concentrating all efforts on the right bank, since it seems to be running lean.

The problem:
has thrown a P0171 codes (lean on the pass (right) bank 1)
rough idle, loss of power
Long term fuel adjustment on bank 1 is very high, 20%+, bank 2 is around -4%

What's been done:
During replacement:
Timing set replacement (4 chains, tensioners, guides)
new idler pulleys, new belt tensioner pulley
new water pump
new gaskets and seals (timing cover & valve covers)
replaced vapor feed lines (they were gross)
After startup, and new problems noticed (‘throw money at it’ phase)
removed and bench cleaned all fuel injectors (new o-rings)
new coil packs
new PCV valve

Things I know, or have been tested:
It's not the PCV elbow rubber that is the usual suspect of this
cold compression test showed right bank all very near 210 psi (didn’t test left)
noid fuel injector test showed good (well, all the blinks)
cleaned (correctly) MAF sensor
removed all right-bank lash adjusters and inspected- all good. Cams seem to be just fine.
Smoke test showed no vacuum leaks we could see
‘tested’ O2 sensors by squirting carb cleaner into vac system and watching voltages- correct results
right bank (1) O2 sensors is all over the place. left bank is much more level. (picture)
vacuum: little floaty around 16-18 (this might be a hair low)
no exhaust leaks I know of- it’s quiet

things I could still test/do:
swap the O2 sensors from side to side (doing that now)
replace fuel filter (reported fuel rail pressure (ODB) is constant at ~40psi, should be fine)
replace MAF sensor- baro and temp both a little high, but not crazy. Resting voltage is within spec, but getting close to not being (assume MAF would affect both banks)
test exhaust leaks (this is doubtful due to how quiet it is)
swap injectors from side to side

Last edited by hunterhicks; 06-12-2018 at 03:12 PM.
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Old 06-12-2018, 03:00 PM   #2
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step one: pull cover and verify timing is correct, and the VVT arms are not bent.
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Old 06-12-2018, 03:11 PM   #3
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VVT? This is a DOHC 4v. I should put that in the post above.
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Old 06-12-2018, 03:19 PM   #4
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oh, duh. I was thinking about the 3v. Sound like it's a tooth off.
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Old 06-12-2018, 03:36 PM   #5
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Agreed, verify timing is all correct. If you didn't remove the intake, vacuum lines, etc, then I wouldn't expect any of that to be an issue. The factory cams (at least in the older 4 valve stuff) have pressed cam lobes, I've heard of them moving but I'd think it'd be unlikely given the nature of what you are saying happened.

As far as scan tools go, you'll have to verify the mechanical stuff before digging too deep into the computer side. Don't overlook something simple thinking that a scanner will give you the answers, it'll most likely send you chasing something else no related. I'd agree with checking the right bank first since it's the one with the fuel trims maxed out. If the left bank is normal of near normal it's probably ok.

I seem to remember an alignment pin or dowel for the cam to cam gear alignment, make sure you didn't damage or smash that so that it's not aligned correctly.
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Old 06-12-2018, 03:49 PM   #6
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You have a lot of post.
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Old 06-12-2018, 03:53 PM   #7
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besides yanking the front cover off, any ways to check timing on this? I've researched it, but don't see anything on it. You can see the cam sprockets and main chain/sprocket with the valve covers off... but that crank sprocket...

I'm getting a solid 210 psi cold compression, which I would think would point to the timing being ok, but may be mistaken here.

this is the time I'd like some more electronics to spit out answers for me.. not exactly a fun teardown.
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Old 06-12-2018, 05:04 PM   #8
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And yeah, that is a lot of posts!! That's funny.
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Old 06-12-2018, 05:26 PM   #9
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Quote:
Originally Posted by hunterhicks View Post
And yeah, that is a lot of posts!! That's funny.
I got you, fam.
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Old 06-12-2018, 10:30 PM   #10
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No easy way, tear it down and double check the mechanical marks or count links, etc. Being off a tooth won't affect compression enough to notice but throws the valve timing off enough to not function right. You should be able to check the secondary chain alignment with valve covers off, that's about it.

And lille I said before, the scanner likely won't point you in the right direction aside from what you already know. There's no magic box that tells you what's wrong contrary to the general public"s thoughts. If it had a cam sensor on each bank you could over lap the cam sensor signals along with the crankshaft position signal using a multi channel labscope and possibly see the variance in cam timing if it were off, but even at that you'd have to know where the signals should be in relation to crankshaft position in terms of degrees, etc.
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Last edited by shumpertdavid; 06-12-2018 at 10:35 PM.
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Old 06-14-2018, 09:53 AM   #11
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I used the Ford timing kit when I had to fix my 4v. Canít screw it up with that. Not very forgiving if it was turned over with wrong timing set. Not saying thatís the problem but possible. Also would check for intake leaks on that side. I had the wrong intake gasket installed on mine and it missed real bad. Guy at shop where I had cylinder heads worked gave me two exhaust cams in one side and all kinds of shit. Definitely use the Ford timing kit itís very simple
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Old 07-18-2018, 12:30 PM   #12
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Made a video of it doing it's thing. While it does report a misfire in the video, it also does this when not reporting a misfire.

https://youtu.be/tfnbCYUN4pY
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Old 07-18-2018, 12:36 PM   #13
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Damn man, that is an outstanding video. I'm sure that would really help me a lot if I knew dick about these engines, lol.
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Old 07-18-2018, 01:28 PM   #14
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I believe you need to do a leak down test and see if you have a cylinder with heavy loss. I'd start on the bank that is adding the most correction to fuel trims. You can do a compression test to start with but it may not show much change if you have a lightly burnt/bent valve or valve spring broken.
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Old 07-18-2018, 08:01 PM   #15
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Quote:
Originally Posted by hunterhicks View Post
besides yanking the front cover off, any ways to check timing on this? I've researched it, but don't see anything on it. You can see the cam sprockets and main chain/sprocket with the valve covers off... but that crank sprocket...

I'm getting a solid 210 psi cold compression, which I would think would point to the timing being ok, but may be mistaken here.

this is the time I'd like some more electronics to spit out answers for me.. not exactly a fun teardown.
210 psi on all cylinders or did you only test one? I would test all 8. If one bank timing is off you might see different compression from bank to bank.

I think you could also theoretically use a degree wheel to compare timing from one side to another.
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