7.3 slight miss, knock, but compression and injectors seem OK... What could it be?

[greenskeeper]

The heater works, but I haven't tried it in this case. I can say that in the summer when it was hot it smoked just a little, I'd say not much. I'll try the heater now, for comparison.

So what would this tell you?

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If you plug it in and it doesn't smoke, it could be two things.

glow plug system has issues

injectors have issues, mainly the armature gap which can cause an issue when the oil is cold and thick.

OR ANOTHER THOUGHT...could your fuel system be sucking air causing the smoke/knocking ?

 

[QuercusRubra]

Not suckling air, I'm pretty confident. I resealed and fixed all that stuff, and I have a fuel pressure gauge, so I think I'd notice fluctuations if it was suckling air.

That was the problem in the first place, though, I bet.

Whick brings me to a question: what internal damage would be caused by an injector that was messed up by sucking air?

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[13fcolt]

I had a similar issue on my 01 excursion. Chased it for months, everything I could think of, bent valve, pushrod, bad injector, wiring harness...etc truck ran fine, just the sound that was louder sometimes or not even there other times. just before I finally found it, it had become constant.

Sooo I did a power steering pump swap and discovered the lower pump bolt was backed out as far as it could. It would click against the holes in the pulley and the rotation would sometimes spin the bolt back in enough, making the sound diminish or go away. Only damage was a shallow groove inside the pulley and a slight chamfer on the bolt head.

 

[paramax55]

Along those same lines... I didn't mention it because you said it was running rough and you are sure it's coming from under the valve cover... I had a rod knock - I was sure of it. So sure, in fact, that I pulled the pan and replaced the rod bearings (yes, you can get the pan off with the cab on, but it's not easy). Guess what? The knock was still there. I could pull injector plugs and get the knock to change, but it would be on different cylinders at different times. The next time I cleaned the injectors, the knock was gone (for a while).

But the truck never ran bad...

 

[QuercusRubra]

Mmmm. That's a good thought. I should go around checking for loose bolts and such. I wouldn't say I'm sureits under the valve cover, it's just what I've come up with, especially with the cct failure. At the moment I'm leaning towards a weak cylinder 4 and idiopathic cylinder 8 cct failure that's a known issue.

I was wondering if the ringing knock sounds I get could be dual mass flywheel failure, but I haven't confirmed if I have one. It feels like a Ford clutch.

I've looked for something that's rattling or vibrating against something, but I haven't found anything. Usually I would expect someth you can flex and make the noise start or stop...

I had a similar issue on my 01 excursion. Chased it for months, everything I could think of, bent valve, pushrod, bad injector, wiring harness...etc truck ran fine, just the sound that was louder sometimes or not even there other times. just before I finally found it, it had become constant.

Sooo I did a power steering pump swap and discovered the lower pump bolt was backed out as far as it could. It would click against the holes in the pulley and the rotation would sometimes spin the bolt back in enough, making the sound diminish or go away. Only damage was a shallow groove inside the pulley and a slight chamfer on the bolt head.

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[13fcolt]

I was certain my clicking sound was coming from under the valve cover. Drivers side, right behind the alternator. I swapped that injector to the passenger side. noise was still there. sticky lifter? nope. I overboost on occasion so valves and pushrods were likely culprits as well, but all good there.
It was super frustrating to live with and not have it sorted out. I just knew it was going to grenade on me in the middle of nowhere. it was one of those occasions i really missed my idi, I knew all of her sounds.
When I pulled off the accessory bracket and saw that pump bolt, a little light bulb went off. gave the pulley a spin and heard that familiar sound. I laughed at myself so hard had anyone witnessed it they'd have thought I'd lost my mind again.

Passenger side click was a bad ac clutch bearing. that one was easy because I could observe it when running.

 

[Skidtech]

Don't know if you found your answer yet but I had a similar set of symptoms once and it turned out to be a cracked injector cup. Make sure you check your coolant for fuel. I also don't recall if this was said yet but make sure to check all the injector and glow plug wiring over very closely because those valve cover harnesses have a lot of problems.

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