My 2016 Mazda3 with 120K miles on it has a weired issue, when i brake and then accelerates i smell a wiff of oil burning smell. Also smell the burning when I'm going uphill from stop.

The smell doesn't come all the time, can't smell anything under the hood or in the exhaust.

The other day i parked the car and reved up a bit to see if i can smell, but nothing. What could it be?

 

Time to pull the spark plugs and have a look. Also look at the inside of your tail pipe. Not as easy. The intake manifold may have a buildup of oil from the PCV system. You can scope it or pull it and do a service cleaning. You could have a small oil leaking? Laying cardboard after a good drive may give a clue if you do and a starting point to look where it is coming from?

Beyond common since items, I mentioned without more testing it really hard to say just from what you posted.


You could simply have worn out guides in the head or worn piston oil rings.... all these can be tested to find out before assuming anything.
I would start with what I mentioned in the first line.

 

120k Miles. Did you do your timing belt recently? Your camshaft seals could be leaking which is why you cant see anything around the engine cause it would be all hiding behind your timing belt cover. Your engine mounts could be worn out as well since you saying you smell it when you brake then accelerate or going up hill. Maybe worn mounts causing uneccessary wear on other parts of the engine. Do you feel any weird thuds or hear vibrations when car is idling or driving under load?

 

No timing belt in petrol Mazda 3's.

 

true, i wanted to buy one but all the second hand ones I see have engine knock at high rpm so I figured bah must have a suck engine.

 

The only thing i changed are the following,:

Spark plugs and wires at 90K
Regular oil change at 4 to 5K miles
Radiator flush at 120K miles just done recently

Plan to do:
Drive belt
Transmission fluid check Midas (USA)

That's all Mazda book recommends.

 

A thought only....
Hey grim what do you think about possible oil puddling in the intake that has accumulated over time from various operating condition? One idea, it may have been caused from the PCV system and the OP just now noticing it? The only way I would think to confirm this unless you have an idea is to pull the Throttle body have a look inside and maybe even run a scope and have a look?

 

Possible.
Inspection camera/scope would be a good idea.

 

Did you check there was no oil leaking off your filter? Sometimes tight when you do it comes loose later and lil line of oil leaks unless you tighten it up a lil more. Did you remember to line your filter with oil before refitting?
If I were you id pop the car on jackstands and actually get a torch under there. Youre bound to find a leak or signs of where oil is coming from. Might also just be residue oil that spilt on the engine when filling her back up lol.

 

Couldn't find any oil leak but encountering a new problem.

In the morning i hear a sound of water gush when i start the car and accelerate. I wonder if the smell of burning oil and water gush could be a sign of head gasket?

No sign of foamy oil or white smoke from tail pipe may be an early stage? Who knows? The car has 120k miles