Ok so i have always had this tick not a knock but a tick in my engine. It doesn't bug me normally and i have read a ton about these ticks but i done think mine is the same as most others.
When i start my cherokee its ticks very softly at idle. A normal person would never hear it. It doesn't get louder or increase in speed with acceleration it actually can't be heard with acceleration. I haven't noticed if it goes away when the engine warms. However I did notice it is coming from the right side of the vehicle (passenger side) about mid motor. If i put my ear up to the valve cover it is no louder actually quieter(kinda rules out a lifter) but if i put my ear in the void space between the inner fender and the engine it can be noticeably heard.
143K Miles, oil pressure stable and good, full coolant, not overheating. runs great.
90 - xj laredo- 4.5" rough country lift, 6.5" of total lift with drop brackets, zj disc brakes on c8.25, olympic winch bumper, jcr upper and lower quarter armor, IRO hack-n-tap and rock sliders and rear bumper. rugged ridge 8500lb winch. Spartan locker up front. With a jd yellow paint job, 97+ front end and bushwacker cut out flares. 35's
I believe its the evaporation purge solenoid. Its supposed to tick but not continuously. Mine isn't horribly loud but I can hear it when I pop the hood. If yours is noticeable inside the car then I would check the mounting bracket to make sure that thing isn't touching the A/C line of the firewall. If it is, then that could make the sound inside the car.
Also, you should take a close look at the vacuum lines running to/from the solenoid. Any leaks in the lines will cause the solenoid to run longer than it would otherwise.
It could be this little thing. Mine ticks all the time. I just tune it out now ha.
I actually have now confirmed its that evaporation thingy. I turned the jeep on and everything ran no noises. 2 minutes after running tick tick tick tick tick and i go over touch the little cylinder evaporation thingy and yep clicking away at the same pace. SO that was my engine noise.
I had some ticks when I got the XJ. Using marvel mystery oil in the crankcase each fillup has eliminated all ticks the engine had. Ive had to use a quart each oil change, because if I dont they come back. However, it really has made a difference in the quietness of the engine.
Owner of a 1 owner 93 XJ county trim, 4.0, AT, 8.25 rear and 3.5 gears. It has goodies like pw/pl, cc, tilt, cd changer, keyless entry, rear wiper and defrost...overall a nice old jeep, my fifth owning previous wanglers and commander
[/COLOR] also own/restored a 1972 Pontiac Lemans GT originally owned by my grandmom....39k original miles. my 72 pontiac musclecar