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.