2004 Mazda6 Burning Oil Smell and Sluggish Acceleration

Car Details:
2004 Mazda 6 V6 3.0 L engine automatic transmission with 88,000 miles

Car Problem Vignette:
After driving for a bit, say 20-30 mins (after my engine gets hot), I start to smell a burning oil smell. I’ve looked under the hood at my engine and do notice some oil leaking from the engine. This is not just some simple oil leaking after an oil change. The oil appears to be coming out of the engine “seams” itself. This has persisted for some time now. This problem started at least a year and a half ago now (12/05/12). I’ve had a mechanic take a look at the oil leak and supposedly he fixed the head gasket or valve cover gasket (I’m not sure which one), but the problem never fully resolved.

In a related or unrelated situation (I’m not sure yet if it is related) during this time my car started to jerk and sputter when I drove, so much so that I wasn’t sure it was going to make it to work one morning. The check engine light came on and thankfully I eventually made it to work and back home that day. It gave me a code that said one of my cylinders was misfiring. I proceeded to change all of my spark plugs to no avail. I then changed out one of my ignition coils to the bad cylinder misfire. It fixed my problems with the stuttering and I could drive my car again without fear of stalling. However, I still smelled burning oil. Over time I eventually started to feel my car struggle to take off during acceleration which felt different from when my car seemed like it was going to jerk and sputter to a stall. During this time frame one day I was at a stop light and when I went to take off, a huge plume of bluish / white smoke came out the exhaust and I smoke-screened the people behind me. After that incident, I ended up changing my positive crankcase valve (PCV). After changing my PCV my car felt like brand-new again! I could not believe it! My car started accelerating smoothly and driving so much better. I felt like I had gotten the “Zoom Zoom” back for my Mazda.

Sadly this didn’t last long, maybe a month at the most. My car started struggling during acceleration again and I started smelling burning oil again. I have dealt with this for over a year now. My car still runs and gets me around, but I can’t remember the last time that my car ran smoothly or didn’t smell like burning oil except for that time I changed the PCV. I have never seen any kind of smoke coming out of my exhaust again like that one experience.

• Burning oil smell coming from my engine due to leaking oil coming out the “seams” of the engine

• Car is struggling when accelerating especially at lower gears

• I feel it every so often when I accelerate somewhere between 2nd and 3rd gear that the car jerks and makes this “chunk” type sound and feeling when it shifts gears.

What is wrong with my car? Are all these situations related? And what do I need to do to stop the oil leak and acceleration problem?

Please check your repair invoice to determine whether the head gasket or the valve cover gasket was replaced. There is a major difference in both cost and severity of problems between these two types of repairs.

At this point, my best guess is that the burning oil smell is from oil seepage coming from the valve cover gasket, and leaking onto the exhaust manifold. However, that would not explain the acceleration problem.

So, it is also possible that the oil seepage is coming from a head gasket (your car has two), and in addition to oil seepage, head gasket problems can result in a whole litany of problems including low engine compression and–even more important–contamination of the motor oil with coolant.

Please pull the dipstick and tell us about the condition of the oil.
Does it look like motor oil (either clean or dirty), or does it look like a chocolate milkshake?
(the latter is the tell-tale sign of coolant dilution of the oil)

If I was in your situation, I would have a compression test done on the engine, and I would also have the coolant checked for evidence of combustion byproducts. The mechanic’s “sniffer” for checking emissions can be used to see if there are combustion byproducts in the coolant.

The “clunk” and the “jerk” could be an indication of transmission problems, in addition to engine problems, and if you have both types of problems, the total repair costs could make it unrealistic to repair this 10 year old car.

In addition to reporting back to us regarding the type of gasket(s) that were replaced, and regarding the condition of the motor oil, please report the level, color, and odor of your transmission fluid.

We also need to know what types of maintenance the car has had over the past 3 years.
Additionally…if the Check Engine Light is currently lit-up, please report back to us on the diagnostic trouble codes that were found.

Your car needs a good look-see including a compression test. It has all the symptoms of a worn out engine.

The PCV valve got gummed up and oil is weeping past the seals because the crankcase is being pressurized by “blowby”, which is combustion gasses being blown past the worn out rings & cylinder walls and pressurizing the crankshaft. Since the crankshaft is openly connected to the space under the valve covers, that pressurizes everything and forces the oil to weep past already-tired gaskets and seals.

The aforementioned loss of cylinder pressurization also makes the engine too weak to operate properly. It struggles.

That cloud of smoke you left at the stoplight was probably from oil leaking down past the valve stem seals. The rocker arms and their corresponding parts get lubricated with oil and it normally just runs down the return tubes back into the crankcase. The seals normally keep the oil from getting drawn into the cylinders.

You don’t have that many miles on the car. Usually this type of premature wear is caused by lack of maintenance and/or failure to monitor oil levels. Just an FYI.

I hate to be the one to say it, and you should take it to a shop to see if I’m right, but I think your engine is shot.

Thank you VDCdriver and the same mountainbike for your quick and thorough responses. Your description of the problem, the same mountainbike, sounds like what I thought could be the problem as well with worn gaskets and seals.

I’ve checked the oil and the oil level is fine and the color is fine. It doesn’t look milky at all. It is just a dark brown dirty oil color.

However as I was checking fluid levels in my car, I did notice that my coolant levels were a little on the lower side so I refilled it. I have noticed that I have needed to replace the coolant levels on occasion; I may have had to refill the coolant 2 or 3 times since this problem began 1 and 1/2 years ago.

The repair I believe after looking back was most likely a valve cover gasket. The cost was around $125 for labor and repair with silicone sealer. The invoice doesn’t specify the exact work done.

Transmission fluid levels are overfull actually. The color is like a dark smoky maroon / burgundy color. The smell is, as best as I can describe it, like fresh asphalt or even kind of like burning oil.

There is no check engine light on currently. The last time I saw the light on was when I had a cylinder misfire and I replaced the ignition coil and spark plugs. Can I still get codes from my car even if the light is not on?

The maintenance on my car over the past 3 years has mainly been routine oil changes, tire rotations, and 1 brake pads and rotors replacement along with brake fluid flush. As mentioned before there was work done for the valve cover gasket. I had a state inspection about 10 months ago that passed emissions test and everything else. I live in Virginia and we have a very thorough state inspection. I’ve personally replaced the PCV once, all the spark plugs once, and one ignition coil. I’ve also replaced and installed a new air filter about a year ago and I once poured some Seafoam into the gas tank to help clean it out. I’ve had a mechanic tell me once that my car needed an induction service done which I was uncertain of and did not do. I’ve had the power steering fluid flushed and exchanged. That about covers it for car work.

If your trans fluid is burnt smelling thats a problem. That should be changed out. As far as reading the level I believe the engine needs to be driven around and warmed up a bit, then with it running check the level on the dipstick. Refer to the manual for checking it. If you do it cold then I think its an inaccurate reading.

As for the lower coolant, this you want to check when the engine is completely dead cold, like in the morning before using it. If the engine is slightly warm coolant may still be in the engine block causing the level to look low.

Outside of all of that, it sounds to me like you have a bad head gasket. That ploom of smoke is from burning something other than gas. If its blueish then I think its oil and if its whiteish its coolant I believe.

Engine needs to be gone over and rebuilt sounds like. You can also transplant used engines usually for cheaper.

Oil smell is very acrid and antifreeze is sweet smelling.

How often do you change your oil? If changing the PCV made a big improvement, try servicing the entire PCV system, especially the vacuum port for the PCV at the end of the hose attached to the valve…Those ports can plug up. A failed PCV can force oil vapors into the air-cleaner box, plugging up the air filter…That might account for the smoke screen you observed…

Valve cover gasket leaks are a pretty common thing. Usually a new gasket fixes the problem but not always. It can be a little tricky. On my Corolla the shop manual recommends to place some sealant at a couple of spots. And to tighten the bolts that hold down the valve cover to the correct torque using a torque wrench. And I think there’s an order you have to follow too. I’ve always followed that procedure to the letter, and never had an oil leak from the valve cover occur afterward. Over tightening the valve cover bolts is a common DIY’er mistake and causes no end to the amount of problems with valve cover leaks.

When the PCV system fails, that can cause oil leaks too as described above, and not just from the valve cover. There’s a UV dye that can be added to the oil and used to trace where all the leaks are originating. Special equipment is needed for this, but most shops have it. That’s something to try.

Loss of power on acceleration is often caused by EGR system problems, fuel pump problems, air filter problems, or a clogged exhaust system, if so, usually it is the cat.

My '07 Mazda has both these same issues. I was assuming that oil is hitting the exhaust manifold causing the smoke. It appears from the engine compartment and escapes thru the hood and thru my Vent into my main cabin. I am also suspicious of the fan motor as the indicator light between recycled air and fresh changes and becomes inactive (unselectable) for some time after.

The shifting problem/chunk is from the car starting out in the wrong gear. My electronic display, if accurate, shows me in a higher gear than I am needing at time of acceleration, therefore the jerky/chunk. I just started switching into the manual mode to verify this. Some days are worse than others.

I have an air bag recall so I might have them do a diagnostic on it and let you know what they say.

1 Like

Thank you for posting this. I am having the same issues and have been stumped as to what the problem is. It could be so many different things without a check engine light, it’s a pain in the rear.
I wonder if it is due to the transmission control module that it is starting in the wrong gear. I have heard Mazda’s have that problem frequently. I know for certain my cooling fan and fan control module need replaced. I am not sure if maybe a short in the module could cause problems in its connected counter parts.
Any updates?