Any other ideas?

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getdealtwith

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I've had a slight (irregular) engine shake on my 2V 5.4 '04 Expedition and was never able to resolve it.

This is somewhat following me on my '04 Navigator with the 32V DOHC 5.4 motor has a relatively smooth cold idle but once warmed up, I get a more rhythmic vibration at 700 (and 1300-1400 RPM) that I just can't "shake"(ha).

When I bought it, I had the engine compression tested (good and even) before dropping money into it because I've heard these engines like to burn the cylinder 8 exhaust valve.

During and after getting the timing chains and tensioners done, here's what's been replaced:

(1) New coils (NGK) and Motorcraft plugs
(2) New intake manifold gaskets (upper and lower)
(3) New Motorcraft IAC (fixing a sticky high idle)
(4) New Motorcraft EGR, cleaned EGR passages in the intake after I got EGR codes
(5) New Motorcraft EGR DPFE (actual cause of EGR codes).
(6) New OEM PCV valve, hoses and vacuum lines (incl. under the manifold).
(7) Smoke checked for vacuum leaks, none
(8) 8 new Motorcraft fuel injectors and rings. Replaced one slightly burnt connector (1 injector was definitely leaking)
(9) New Motorcraft fuel pressure regulator (new fuel filter also)
(10) New MAF sensor (new air filter, as well)
(11) New O2 sensor (all 4)
(12) New motor mounts and transmission mount
(13) High pressure oil pump installed.
(14) New alternator

Before anyone assumes faulty new parts, take a look at this live data screenshot below. Note the short- & long term fuel are well within the +/- 10% range and look really good. To my understanding, this pretty much eliminates even a small vacuum leak the smoke test might have missed. Also: there are no misfires, so I'm not sure there's a problem with the coils.

1651949724943.png

What else have I looked into? - Mechanical possibilities:

- Harmonic balancer (came up during a search for 750 & 1300/1400 RPM engine vibration). Mine looks to be in good shape, there's no wobble and most importantly, the engine idles smoothly when cold.

- Transmission flywheel. I've read about this fixing mystery idle vibrations for others. Problem: the engine shakes in Neutral and Park, as well, not just in Drive.

- Belt tensioner. It moves a little when the engine runs but I'm not hearing noises and the mechanic didn't advise changing it when they had the front open for the timing job either.

- Timing off? - The engine runs and pulls strong.

The only thing I haven't done yet is a leak down test to see if one of the cylinders isn't sealing well.

Anything else I might be missing or misinterpreting? - For example the assumption that transmission flywheel couldn't be a problem because the vibration occurs in N or P? (It just seems an odd culprit to begin with but maybe not?) - Replace the belt tensioner and harmonic balancer anyway?

Thanks!
 
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getdealtwith

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It's still not idling 100% smooth but I found a loose upstream O2 sensor finally triggering a code that probably allowed air into the exhaust. Any remaining shakiness in the idle from here has got to be mechanical. Engine has 162K miles but was driven by the PO with worn / busted timing chain tensioners for 20K miles (discovered on a diagnostics bill after purchase) and probably shavings or debris in the oil + ****** 5W-20 in the pan. There maybe some wear in the valvetrain causing this but since compression has been good and even across all pots, I'm going to close the books on this but thought I'd share my findings here, also.
 
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getdealtwith

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So, it turns out the downstream O2 sensor in the 2nd bank (driver side) had gone bad, as well. Stuck low voltage signal but no code. (Hadn't looked at that before)

I replaced all with NTK units and reset the PCM. After 150 miles, the idle is completely smooth now.

Leaving this here for anyone looking to smooth out their idle with a strong endorsement for FORscan mode 6 data monitoring. Misfires, injector faults, DFE & MAF sensor function, fuel trims, O2 sensor voltages, it's all there to check before you start replacing any parts.
 

daveinfl33777

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So, it turns out the downstream O2 sensor in the 2nd bank (driver side) had gone bad, as well. Stuck low voltage signal but no code. (Hadn't looked at that before)

I replaced all with NTK units and reset the PCM. After 150 miles, the idle is completely smooth now.

Leaving this here for anyone looking to smooth out their idle with a strong endorsement for FORscan mode 6 data monitoring. Misfires, injector faults, DFE & MAF sensor function, fuel trims, O2 sensor voltages, it's all there to check before you start replacing any parts.
I also have a slight shake at idle that comes and goes and I have gone over everything including up and downstream o2 sensors although I really don't know how quick they should oscillate.

My question to you is did you mean upstream o2 sensor? You mentioned downstream and i thought that downstream o2 (post cat) is just there to monitor your cats efficiency and has nothing to do with engine performance (fuel trims)
 

riphip

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Check rubber vacuum hoses for deterioration/leaking/rotting. 1 or 2 kinda hidden behind battery. Replaced all of mine not long after I bought with 100k on it. Age & heat had done a number on the vacuum lines. ran like a top afterwards like it does now.
 
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getdealtwith

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I also have a slight shake at idle that comes and goes and I have gone over everything including up and downstream o2 sensors although I really don't know how quick they should oscillate.

My question to you is did you mean upstream o2 sensor? You mentioned downstream and i thought that downstream o2 (post cat) is just there to monitor your cats efficiency and has nothing to do with engine performance (fuel trims)
The downstream sensor was definitely bad. Unfortunately, that didn't fix the intermittent idle vibration completely. I ended up changing all plugs again and found that the cylinder #1 coil (1 year old) was toast after a blown radiator caused an overheated engine this summer. Since, I also developed a rod knock and had the engine rebuilt. It still has a minimal shake during warm up in D gear now but I'm not going to worry about it.
 
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