First off i want to say im a Radar Mechanic in the Army so i mechanical skills and troubleshooting skills are greater then the average bear, however automotive lingo gets me sometimes so try and keep me down on earth.
Basically
I have a 4 cyl 2001 mazda 626, it started to make a ticking noise after running it low on oil, it ran low for about 400 miles, i didn't know this but somewhere along the 400 miles it leaked about 2 quarts of oil out of an improperly sealed oil filter. The Check engine light came on and off for about 2 days, no oil light came on, i couldnt figure out what it was. Then i started to hear a faint ticking noise that sounded like a clock ticking. So i decided something was wrong, took the car home and let it cool off. Then i checked the oil and saw it was low. I have no loss in power. wondering what it could possibly be i decided to poke around a bit see if it was something not so serious. I changed out the oil, replaced the filter, put 30 weight in it, nothing changed, still that ticking noise. Figured it couldn't be the exhaust leaks because it sounds a little more mechanical although it is more noticeable at idle when the engines warmed up. So i dug around on the computer. heared about something called cheap feul noise. Not knowing what cheap feul noise sounded like i decided to investigate anyway, hell i had time on my hands. Apparently an Airflow sensor can cause this type of sound so i decided to check the airfilter and the MAF. It was loaded with pollen, since i have a reuseable airfilter i washed it dried it. Put it back on. Still that noise. Decided to dig deeper, checked the MAF sensor, For some reason when i disconnected the MAF and the airfilter and let the engine unrestrictedly take in some air, the sound became MUCH MUCH less noticeable. Figured that its just masking a problem. So i pulled out a big oldratchet and starting stethascoping around untill i centralized the sound, it seemed to be coming from cylinder 1 or 2 couldn't figure out which one. Then one by one i pulled spark plug wires off. getting to spark plug 2 i noticed that when i pulled it off and turned the car on the problem was TOTALLY gone, as in no sound. Swaped plugs and wires around just to be sure it wasn't a spark knock or a bad wire internally arcing, still same noise. Now that i have narrowed it down to cylinder 2 im wondering if its a tapping valve, im excluding a cylinder because it doesnt sound like a cylinder at all nore is there any loss of power and can't be a rod because its not knocking, don't think its a bearing because of where the sound is located, maybe an exhaust valve of some sort? Im thinking maybe so because the sound grows in decibles when i depress the gas. What is my next course of action, i really don't want to play with 1000 dollars if i dont have to. Is my next course of action removing the valve cover and poking around, if its an exhaust valve where would i start? I read somewhere that some people remove their valve covers and run the car at idle to visually inspect the car, however im not a daredevil and don't wanna do it without second opinions. I have also heared that sometimes with mazda's a screw can come loose off a butterfly valve in the exhaust and get sucked up into it and cause it to rattle around in the engine. What would you suggest my next course of action be? Any information would be greatly appreciated.
Thanks
Chris

 

Marvins Marvelous Mystery oil in the crankcase and Techron in the fuel tank then run the hell out of it. If that does'nt do it you will need an HLA most likely. At least you have isolated it.

 

My DSM's valve lifters would tick a lot sometimes until they got good and oiled.