New Engine, Same Knocking

I own a 94 4x4 ext cab with a 4cyl, stnd, KA24E engine. I recently had the misfortune of having Jiffy Lube cause a rod to be thrown in my engine. It had 176,000 miles. Jiffy Lube or rather Engine Muscle came through with a check for 2 grand to my mechanic to replace the engine. He purchased an engine from Greenleaf Parts in Dallas. It had 108,000 miles on it. I believe he got the full block ( for $800, it should be, right?). Before all this happened, I had noticed a rattle or ticking coming and going. It could start on the freeway and maybe 20 miles later it was gone. I had thought it was a lifter sticking. However, now having a different engine in it, I don't know. I took it for a mini road trip Saturday and it made the noise within 20 miles of freeway driving and soon dissapeared, reocurring throughout the day. Where should I start looking for the "Knocking" problem now that i have a different engine? Could it be the O2 sensor, fuel filter, PCV valve, new plug wires, cap & rotor, what? Any help would surely be appreciated. Thank You.

I'm no expert, but if it's a 'tick' and not a 'knock' I'd look for something hitting your fan. My buddy had an old mustang and the battery tray was so rusted it would bump the fan around corners. Just a thought. If not, and they did replace the entire head (valves, lifters etc.) only thing left I can think of would be the tranny. Hope this helps.....

Thank You avpdrmr,
I will check that, however on observation, the noise seems to be coming from tne top of the engine. I'll keep trying to get to the bottom of it. Thanks again.

if it is a tick you may need to have the valves adjusted. it may even be an injector tick highly possible with nissan injectors

[jtesensky]

I would think about the timing chain. When the chain loses tension (possible new tensioner) it will smack the side of the front cover, and it can be inconsistant like you described.

My 94 ka24e pickup has a throw-out bearing that will not shut up. When under slight engine braking, it will chatter like chain noise or top end noise. I believe there is a service bulletin on this.

[nizmo559]

Maybe your ECU is about to die.