Rhythmic tic that comes and goes

Usually with any ticking or tapping coming from the engine, I want to listen at the valve covers and oil pan. Use a mechanics stethoscope to listen, see if you can pinpoint where the sound is coming from? You could also listen at the housing of any belt driven component, just don't get anything caught in belt or pulleys.

The sound is coming from the front left side. But why the coming and going of the sound. Around 140deg the tap is gone. If it was a piston slap it would be constant till warm up along with lash adjuster tap. An exhaust leak would also be constant Untill the heat expanded the leak closed.

Could have a bad lifter so when it warms up and the oil thins out it pumps up easier and the noise goes away.

If it were a bad lifter it would tic all the time till warmed up. But this tic comes and goes till it disappears once it's warmed up.

Not necessarily, How is the oil change? old oil can cause this as the viscosity diminishes engine components will make noise, the rhythm you are hearing is because the lifter is rotating in its bore.

Please let us know what happens

Changed oil and filter. Still have my tic. At start up there is no tic. Watching the obd2 reader the tic starts when it comes out of its closed loop mode. As soon as the ecm starts to accept info from the o2s the tic starts. If I turn off the engine in the middle of a tic sequence and start it right back. No tic Untill the 02s start bouncing around again. Once it hits around the 140 deg mark it just purrs.

check the knock sensor its the only thing I can think of that would cause any noise but would be very strange. And it goes into closed loop

This sounds like a sticking intake or exhaust valve when the engine starts to warm up, this would account for the 02 fluctuations when the tick is occurring. It might be time for a valve job.

Ok. Thanks for all the input. Still have the tick. It still runs smooth Untill the full trim picks up. Now I tried something here the other day and this is what happens.
At cold start. Initial cold idle is 1200 rpm as it warms up the idle decreases. At stat up its purrs perfectly. When the rmps hit around 1000 i starts to get my tic. I Rev it back up to 1200 and hold it steady. tic is still there. Let it go back to idle. 1000 rpms. Tic still there. I turn off key and immediately restart engine. No tic. Again rmps go to 1200 then falls back to 1000. Then tic starts. No I let it tic till the tic gets pretty loud. Again I shut it off and start it right back. 2 seconds max between running off and running again. No tic. 1200 rmp falls right back to just under a 1000 now. Engine timp is now around 120. She starts to tic. Again I wait for the tic to get fairly load. I can here the tick slash knock from 20 feet away. I repeat. Every time I start it back up the tic is gone until the fuel trim starts.
If it were piston slap or lash ajuster wouldn't it start tapping as soon as I start it back up. Could it be detecting a noise. Then in the process of tring to get rid of it by changing fuel trim and timing it is making it worse?

FOR WHAT IT'S WORTH (SOME PEOPLE DON'T SUGGEST ADDITIVES- I'M DIFFERENT!)

NEXT OIL CHANGE SUBSTITUTE 1 QT OF MARVEL MYSTERY OIL, FOR A NORMAL QT OF OIL YOU WOULD NORMALLY PUT IN (NOT ADD A QT, AND BE OVERFILLED BY A QT!). WHILE YOU ARE DRIVING, "MMO", MAY CLEAN IT UP, "MMO" CAN BE LEFT IN, UNTIL NEXT CHANGE...OR YOU CAN RUN A NEW BATCH....READ THE BOTTLE!

IF YOU GET IT TO QUIET DOWN, YOU MIGHT DO WHAT I DO, I USE OIL STABILIZER EVERY OIL CHANGE IN MY 1977 JEEP CJ 5. I DRIVE IT ALMOST EVERY DAY, AND I REBUILT THE ENGINE IN '96, IT IS STILL GOING STRONG. (I DID NOT USE THE STABILIZER UNTIL MY 4TH OIL CHANGE, I WANTED TO INSURE MY CYLINDERS WERE BROKE IN WELL AT ABOUT 12,000 MILES).....I HAVE NOT HAD ANY TAPPET ISSUES WITH THIS ENGINE, BUT I HAVE USED THE "MMO" ON PREVIOUS CJs I HAD

I HAVEN'T HAD TO USE MARVEL MYSTERY OIL IN MY PRESENT CJ 5....I HAVE HAD 5 OTHER CJ 5s PRIOR TO THIS ONE, THE MMO, HELPED WITH SEVERAL OF THEM. I HAD ONE THAT WOULD NOT STOP, I USED A LITTLE MORE DRASTIC MEASURE WITH IT, BY INSTALLING A PUSH ROD A FEW THOUSANDTHS LONGER THAN THE ONE THAT WAS PUSHING ON THE ONE THAT WAS DOING THE "TAPPING". THAT SORTA JUST RE-POSITIONED THE PLUNGER INSIDE THE TAPPET AND IT BEGAN "SEALING" AS IT SHOULD, AND THE TAPPING CEASED.

IT ONLY TAKES A LITTLE STUCK ON BURNT LOOKING OIL ON THE THIN STEEL DISCS INSIDE A TAPPET TO KEEP A TAPPET FROM SEALING.....I'D TRY THE MARVEL MYSTERY OIL 1ST, BEFORE GOING ANY DEEPER. DO OT OVERFILL YOUR OIL, DRAIN OUT A QUART, THEN INSTALL A QUART OF MARVEL MYSTERY OIL

THIS STUFF HAS BEEN AROUND SINCE WWII, YOU CAN FIND ENDORSEMENTS ON YOU TUBE, BEATS TEARING INTO ONE!

THE MEDIC

I've used the mmo, sea foam, had a bg flush done. I thing what's happening is I've got some lite piston staple when it's cold. The Knock sensoris picking it up and is to correct it by changing the advance. This is causing an ignition ping which gets louder the more it try to get rid of the knock caused by the piston slap. Till it gets to a point where it then resets it's self to start the hole process over to try to get rid of the piston slap. As the piston slap goes away as it worms up the knock senor doesn't pick it up anymore and every thing is fine.

ONE OF MY FRIENDS HAS A 2000 GRAND CHEROKEE 4.0 L, HE HAD A LITTLE "MORE THAN A TICK" GOING ON.

THEY DROPPED THE PAN, FOUND A CHUNK IN THE PAN, LOOKED UP IN THERE AND PART OF A PISTON SKIRT HAD BROKEN OFF.

NOT TRYIN' TO SCARE YOU OR NUTHIN', JUST THROWIN' OTHER POSSIBILITIES

THE MEDIC

Well finally found out what is going on. Dealer and I both agree.
Slight piston slap is triggering the knock sensor. The tic that gets louder is the computer trying to get rid of the piston slap. But in its attempt to stop the piston slap it is causing spark knock. The reason it stops for a little while, is because it reverts back to a a neutral timing. Then it picks up the piston slap again and restarts the sequence to try to get rid of it. Once motor warms up enough to stop the piston slap. The Knock sensor no longer detects it so no need to a just the timing which caused the spark knock.
Cure is to stop Piston slap.

That makes sense, today's engines are built with shorter pistons with do make a little noise, good find I hope we helped please use 2Carpros anytime we are here anytime :)