My wife has a 2010 Mazda 3 5 door, 2.5 L with about 73,000 miles. Everything has been great up to this point.
Saturday we drove up to NY from Virginia. Everything was great.

Driving back from Syracuse NY to Virginia Monday started to hear a knocking noise coming from the engine area over 60 mph when I stepped on the gas. If I slowed down to around 40-50 and hit the gas nothing no sound.

I thought maybe low oil but no oil light and the oil was just changed 2K ago.

If I pulled over for gas and waited a bit and then got back on the road I didn't really hear the knocking sound fro about 10-20 minutes. Seems like the car had to get all warmed up again. Very puzzling...

Again below 55 ish I dont hear anything when hitting the gas. Only above 60ish and only after I have been on the road for a bit....drove into work today and went over 60 and hit the gas....didnt hear anything...only 10 minutes to work and all under 50 so I never hear anything.

Anyone ever see this before?

Bearing? Axle? Rods? Air Conditioner Condenser? I figure I would hear at all speeds correct

Anything I can test?

PLEASE HELP.....Thanks

 

Is there anything else happening at the same time? steering wheel vibration?

It could be the tires. Rotate them and see if the problem moves with the tires. Also try to describe the noise a bit more. Does it sound dull or tinny, does it have a rhythm, does it occur on hitting minor bumps anything you can think of.

You could go under the car and tap a few things with a rubber mallet. Maybe you find something that makes the same sound.

 

I drove again to work today but never get over 60 mph, where the sound started. It almost sounded like a diesel engine knocking sound.
we did recently have tires put on but drove for 700 miles with no sounds...I cannot imagine the sound coming from the tires.
If a wheel bearing I assume I would hear at all speeds and would be a whine or a constant hum.

Only on acceleration
Only above 60 mph, fine below 50 mph
Nothing to do with bumps, occurred whole time during acceleration
Seemed to occur once on the road for 10-15 minutes
Seems to be coming from the center and bottom of the engine compartment
I dont remember the steering wheel vibrating

Going to take a drive in the next day or so to test out again. Very weird.

Thanks for your thoughts...hmmmm

 

Difficult to tell.
At the first post you were talking more about suspension , now you are talking more about engine.

How many miles ago did you do the last tune up?