Ticking noise that goes away when you disconnect fuel injector

Ok, so I have been fighting a issue with, up until now, I thought was a ignition issue. But after yesterday, now I am not so sure. You can read my thread here for what I have done up until now. http://www.gearhead-efi.com/Fuel-Inj...related-issues
I drive my jeep yesterday to go to the store since it had not been run in about a week or more. It seems to be running a little rougher, still popping out the exhaust on decel, and backfiring with each shift. So late yesterday afternoon, I decided to swap out my current 8 pin module with a spare known good one I had. I figured what the heck, it's a quick swap. Well it made no difference. So I decide to wiggle some wires with it running just to kill a little time. Well when I open the hood, I noticed a ticking noise that was not there before. Walking around, it is definitely coming from the left side, as you can not hear it standing on the right. I check plug wires and they are all good and connected.
For some reason, I decide to disconnect each fuel injector one at a time to see what happens. I found that when I disconnected #3, the ticking went away (same cylinder numbering as a chevy, just fyi). Hook it back up and the ticking noise returned. I shut it off and pull that spark plug. It looked good. Nothing abnormal. I compared it to a couple others and they all looked the same.
All made a noticeable difference in idle when I disconnected each injector. However some made more of a difference than others. I tried to take a video, however all I had was my cell phone, which does not have the best mic. It did not pick up the rpm changes very good, but I think you can just tell the ticking noise. You can hear it at the start, I then unhook the injector, it goes away. I hook it back up and you can hear it return. I do this one more time. I hope you can hear it.
https://youtu.be/vpvF5wKk7oY

The noise sounds to be coming from the top end. I googled symptoms of a bad cam lobe and I am starting to fear for the worst, as some of the symptoms seem to match mine. Not sure why disconnecting the injector makes it go away though? I just want a few more opinions. I ran out of time as it was already late when I did this, and I am getting rained out all day today (I am so sick of rain right now). But when I get a chance I am going to pull that valve cover and see what I can find.
I built this engine back in 2005. I have no idea on the miles, as I did not write it down when I installed it. However if I had to guess, I would say between 30k and 50k
AMC 401.
.040 over, stock style cast pistons, moly rings
Comp cams XE256H cam and lifters
All push rods and rocker arms/pivots were new.
Ported and polished heads, 3 angle valve job, all new valve springs. Shaved somewhere in the neighborhood of around .020.
Edelbrock pro flow efi intake and rails, but the rest of the system is 16197427 based mpfi, bosch 4 hole injectors.

Exhaust leak?

depending on the tick, it could just be your injector..... some can get really loud for no apparent reason.

if you really wanted to, you could move that injector to another cylinder to see if the noise follows it.

It doesn't seem like a injector. It's more of a metallic ticking, and seems to be coming from the top end. I am going to pull that valve cover and see if I find anything. If not then I will swap injectors.
It might not be till tomorrow when I get to pull it. My 10x16 storage building/work shop has a leaking roof. It has started dripping on my workbench. Not good. Has shingle now, going to replace it with metal. $250 later :mad1: I have enough to do it. Now I just need to get a friend over here to help with it.

Try a piece of hose as a super directional microphone. Stick one end in your ear, then move the other end around the motor, almost like an acoustical flashlight, to localize the sound. Any sort of small diameter hose will work, clear plastic 3/8" hose from Home Depot, rubber hose, etc. I've used it before to localize sound sources in a cluttered environment. Test it first on a known noise source (like a ticking clock on your kitchen wall) so you get the hang of how useful it is.

A vacuum gauge (or a scope signal on the MAP sensor) is often very helpful in diagnosing cam problems. Worn lobes often show up as smaller pulses on the needle or as a quick needle movement away from vacuum.

Well I had some time this afternoon to pull the valve cover. I found nothing out of the ordinary. I jump the starter solenoid and watch while it's cranking. All seemed to move the same amount. So I go ahead and fire it up and watch things. It was cold out, so it took a bit to get oil out of the push rods. But once the oil started flowing, all the push rods started spinning. I tried to carefully eyeball and compare all the rocker arms, paying close attention to cyl #3, and all seemed to move the same amount. I was not able to put a dial indicator on them. The ticking noise was still there, but it seemed more faint when I was running it with the valve cover off. But it was a cold start and it was about 40* outside. So I'm not sure if it is temp related and gets louder the warmer it gets, or what. I tried the hose trick with no luck.
I brought home my inspection camera from work and took a peek inside that cylinder. Everything seemed to look ok. Cylinder wall still has lots of pretty cross hatching and no scuff marks I could see. I did however notice a little more carbon buildup inside the combustion chamber than I was expecting. Not sure whats up with that. I rotated the engine by hand and checked out the valves when they were open and the exhaust looked ok, but the intake had carbon buildup on top of it (between the stem and the seat) I did not notice any near the seat, so I don't think and has gotten in the seats. I may give it the sea foam treatment once I finish my hei swap.

Quote:

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Originally Posted by RobertISaar

depending on the tick, it could just be your injector..... some can get really loud for no apparent reason.

if you really wanted to, you could move that injector to another cylinder to see if the noise follows it.

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I agree....you might even be able to feel the valve inside the injector snapping open and close.

That just seems very loud for a injector. I did feel it and the other injectors and it did not really "feel" any different. But I suppose anything is possible.
The injectors were brand new when I installed them. Looking back at my pictures, it looks like I went mpfi about 3 years ago, and only driving it on the weekends , I doubt I could have put more than a few thousand miles on it. Is this normal for such low mile injectors? The injectors are bosch 0280155931. I bought them from a guy who pulled them out of a ls1 crate engine that had never been run. They did appear to be brand new and had zero fuel smell to them.
I may try swapping it around with another one if I get some time. But for right now I am going to focus on the hei swap.

On the cars with a noise like that that I checked, it was the piston pin. The clue is to unplug the injector or coil. If the noise goes away it's because there is no more load on the piston.