Oil in cylinders and failed emissions tests

[Multiplier7]

Hi there,

our Honda Jazz 2007 has failed emissions tests, with the shop saying it smells like burnt oil. The Co was about 0.7, the Hc 300-400 and the lambda value a bit over 1 (so the Co and Hc indicate a rich condition and the lambda a lean condition.

When we took the spark plugs out, they had some oil on it and a white tip. We then put a camera into the cylinders and there was some oil on top of the pistons as seen in the attached image.

We have tested for vacuum leaks, exhaust pipe leaks, the EGR valve, the catalytic converter, changed both lambda sensors, changed the air filter, and the throttle body and intake manifold. All seem fine so it seems more likely that the issue is inside the engine.

Can somebody point us in the right direction as to what the problem could be and why oil would be getting into the cylinders/onto the pistons? Could it be the valve seals/ piston rings?

Note that the car drives and sounds quite fine, but the exhaust fumes have been smelling rich with petrol but there hasn't been black smoke coming out.

Any help is greatly appreciated!

[CRC]

These things may or may not be related, but the first thing to do is to try and work out the oil issue.

As you say, there are normally two main ways oil can get into the combustion chambers. It either comes up past the piston rings from the oil in the sump or it can leak down the valve stems from the camshaft carrier.

It's very unusual for a Jazz to be burning oil unless it's very high mileage or has questionable service history with infrequent oil changes.

A compression test on each cylinder would be a good place to start as it might give a clue about how good the rings are.

In general, if a car is burning oil, the exhaust will have a blueish tinge to it, black tends to indicate too much fuel and white tends to be coolant.

Does the car use any oil when checking the level on the dipstick?

When doing a compression test, take one plug out of each of the cylinders, then screw the test gauge into just one. Crank the engine perhaps ten times and see what the pressure rises to.

[Multiplier7]

Hi CRC, thank you very much for the reply.

yes, we already previously did the compression tests as well (sorry forgot to mention this in the original post) and all the cylinders seemed ok in terms of compression. Does that mean that the piston rings are probably fine?

Previously the exhaust fumes were maybe more whiteish (but hard to say because it was also cold); but they did smell like fuel, especially when idling.

Does the oil need to be burning to ruin the emissions values or can its presence in the cylinders be enough to throw off the readings?

Cheers.

[Lord Voltermore]

My experience of oily engines comes from a hobby of  working on cars from the 1930's. Being about 80 years old at that time  these engines were entitled to be oily, but mechanically they were surprisingly similar to the Jazz    Indeed one dodge was to replace the  original 1930's pistons with Honda pistons ! (from a generator or something similar)

You are referring to spark plugs and pistons  in the plural. Are you saying that ALL  the spark plugs are white tipped and oily   and all the pistons have oil on them as in the photo?

  A rule of thumb before the days of  ECU  and emissions testing    was that white plug tips  indicates a lean petrol/air mix, black tips a rich mix or maybe burning oil , and milk chocolate coloured tip just right.    So white tips with a  petrol smell doesnt sound right. (although whiteish plugs are quite normal on modern engine which tend to run leaner and more fuel efficient than years ago.  )
   
Also really oily plugs and cylinders will often be confined to just one cylinder  due to maybe a broken  piston ring, or damaged valve stem, as CRC says. With very high mileage  all cylinders might get a bit more oily    but usually one or two are worse than the others.

Its quite normal for the cylinder walls to be coated with a  fine film of oil.   Its what keeps the pistons lubricated, and why they have oil control rings.    However  if a fault  is  metering too much  petrol into all the cylinders  this can wash the oil off the cylinder walls, and form a thick petrol/oil mixture .It may be this  coating the tops of the pistons and the spark plugs. It  may look like oil  but smell of petrol, or smell of burnt oil after combustion. 

Unfortunately my 1930's based mechanical knowledge doesnt extend to knowing for sure this is the cause, or how to fix it.  But I suspect if you can get the engine running properly and  able to pass emissions tests   it may as a bonus also solve the oil problem. 

[CRC]

Can you remember what the compression test results actually were?

I don't think I've ever seen a piston crown that looks quite like that before. It does look like liquid oil, though the "edges of the puddle" look a bit jagged?

Also, it's hard to imagine how a puddle like that could form inside a running combustion chamber, and if it was liquid oil, I'd expect a big cloud of blue smoke when you started it up and the high flame temperature set fire to the puddle.

It almost looks like a varnish of some sort? I think I'd be looking for a long cotton wool bud to poke down the hole and see if it comes back wet or not?

Certainly burning oil would raise the Hydrocarbons reading and also the CO reading but the Lambda reading is odd as it sounds fine.

A cheap OBD2 reader normally has the ability to monitor emissions data, O2 sensor values, engine temp values, manifold pressure and long and short term trim values.

If you could get hold of that data it would be good.

If it is a puddle of liquid oil, it's unlikely it's come up through the piston rings as any that came that way would be immediately burnt during the combustion ( oil in the bores is like a very fine "fog" of oil droplets)

Puzzling.......

[bill888]

If the photo shows pool of oil on the piston, is it possible oil is passing through worn valve stem seals when the engine is cold and switched off, then dripping past the opened valves and pooling on the piston?

What is the mileage and how much and how often does the oil require topping up?

What grade of oil?  5w30 or 10w40 ?

[Multiplier7]

My experience of oily engines comes from a hobby of  working on cars from the 1930's. Being about 80 years old at that time  these engines were entitled to be oily, but mechanically they were surprisingly similar to the Jazz    Indeed one dodge was to replace the  original 1930's pistons with Honda pistons ! (from a generator or something similar)

You are referring to spark plugs and pistons  in the plural. Are you saying that ALL  the spark plugs are white tipped and oily   and all the pistons have oil on them as in the photo?

  A rule of thumb before the days of  ECU  and emissions testing    was that white plug tips  indicates a lean petrol/air mix, black tips a rich mix or maybe burning oil , and milk chocolate coloured tip just right.    So white tips with a  petrol smell doesnt sound right. (although whiteish plugs are quite normal on modern engine which tend to run leaner and more fuel efficient than years ago.  )
   
Also really oily plugs and cylinders will often be confined to just one cylinder  due to maybe a broken  piston ring, or damaged valve stem, as CRC says. With very high mileage  all cylinders might get a bit more oily    but usually one or two are worse than the others.

Its quite normal for the cylinder walls to be coated with a  fine film of oil.   Its what keeps the pistons lubricated, and why they have oil control rings.    However  if a fault  is  metering too much  petrol into all the cylinders  this can wash the oil off the cylinder walls, and form a thick petrol/oil mixture .It may be this  coating the tops of the pistons and the spark plugs. It  may look like oil  but smell of petrol, or smell of burnt oil after combustion. 

Unfortunately my 1930's based mechanical knowledge doesnt extend to knowing for sure this is the cause, or how to fix it.  But I suspect if you can get the engine running properly and  able to pass emissions tests   it may as a bonus also solve the oil problem.

Hi Voltermore, thank you very much for the reply and tips. I also gathered that it could indicate a lean mixture if they're white at the tips but I guess if newer engines do this normally in newer cars it's hard to say. The mixture from the exhaust smells rather rich so weird that it's lean according to the lambda value and spark plugs.

And yes, all 4 of the pistons look more or less the same with the pool of liquid covering the piston head partially but not fully. And yes, all 8 spark plugs (we have 2 spark plugs per cylinder) look the same with some oil on the thread but not the tip and a white tip, some a little bit more and some a little bit less.

[Multiplier7]

Can you remember what the compression test results actually were?

I don't think I've ever seen a piston crown that looks quite like that before. It does look like liquid oil, though the "edges of the puddle" look a bit jagged?

Also, it's hard to imagine how a puddle like that could form inside a running combustion chamber, and if it was liquid oil, I'd expect a big cloud of blue smoke when you started it up and the high flame temperature set fire to the puddle.

It almost looks like a varnish of some sort? I think I'd be looking for a long cotton wool bud to poke down the hole and see if it comes back wet or not?

Certainly burning oil would raise the Hydrocarbons reading and also the CO reading but the Lambda reading is odd as it sounds fine.

A cheap OBD2 reader normally has the ability to monitor emissions data, O2 sensor values, engine temp values, manifold pressure and long and short term trim values.

If you could get hold of that data it would be good.

If it is a puddle of liquid oil, it's unlikely it's come up through the piston rings as any that came that way would be immediately burnt during the combustion ( oil in the bores is like a very fine "fog" of oil droplets)

Puzzling.......

Hi, I will try to get ahold of the compression test numbers from when we did it (or do it again, it was already last year when we did it), but as far as I remember all the cylinders were within the recommended range found on Google for the Honda Jazz 2007.

And yeah I guess it is more likely then to be coming in from the valve stems due to broken seals since we don't have a cloud of blue smoke. We will check with a cotton bud as suggested if it is oil or maybe indeed fuel (although the spark plugs would have smelt like fuel if so and it was on the threads of the spark plugs but not on the tips really that much).

The lambda value seemed fine when we checked with an OBD reader but the emissions test said it was rich (the emissions test guy didn't remember the exact number because he forgot to print out the exact results). We did check with a basic OBD reader and it failed the emissions test but didn't give details since it wasn't advanced enough but the fuel trim was like 15% or something within the accepted range and the pre-cat lambda sensor value was fluctuating between like 0.1 and 0.7 V (not going up to 0.9 like google says it should), and the emissions test guy said the pre-cat lambda sensor was responding slowly, which is weird because we literally just changed it for the 2nd time in an attempt to fix the problem. So could there maybe also be an ECU or communication problem?

[Multiplier7]

If the photo shows pool of oil on the piston, is it possible oil is passing through worn valve stem seals when the engine is cold and switched off, then dripping past the opened valves and pooling on the piston?

What is the mileage and how much and how often does the oil require topping up?

What grade of oil?  5w30 or 10w40 ?

Hi Bill, yes I also think it's more likely that it's coming from the Valve Stem seals. This picture was taken quite soon after we had driven the car so it is possible as you said. It has about 230000 km on it and we haven't been driving it much so hard to say how often the oil requires topping up since we've only done the oil change once since we bought it; mostly it's been sitting around in the garage with us attempting to fix it haha. I'm pretty sure we topped it up with 5W30 oil as that's what's recommended.

[cavosavosk]

Well, cylinder head overhaul it is i guess. I mean those Valve Stem seals haha. I think they were done on my car aswell, the previous owner complained that the jazz was consuming oil like crazy. The mileage is pretty much in the sweetspot when Jazz likes to consume a bit of oil. Our old 2005 Jazz with 240k -ish km on the clock managed to eat through the whole oil capacity in a year.

Or a thicker oil, 10w40 could help you a bit...

[Multiplier7]

Well, cylinder head overhaul it is i guess. I mean those Valve Stem seals haha. I think they were done on my car aswell, the previous owner complained that the jazz was consuming oil like crazy. The mileage is pretty much in the sweetspot when Jazz likes to consume a bit of oil. Our old 2005 Jazz with 240k -ish km on the clock managed to nutné through the whole oil capacity in a year.

Or a thicker oil, 10w40 could help you a bit...

Interesting, yeah we will maybe change those valve stem seals and maybe the head gasket as well. Do you know if your Jazz was having any emissions value problems as well or just using up a bunch of oil?

[cavosavosk]

We had silver 2005 jazz, which was consuming oil but always passed emmisions (no blue smoke or anything, it just ate through the oil as time went on). But keep in mind that i am from Slovakia, so eastern-ish europe, thus you could get it through emmisions even if it took a lot of attempts haha. And that car is long gone already. Its more than 5years.

Now I have 2003 jazz, which doesnt consume oil (shocking for a Honda!). But i believe either piston rings or valve stem seals were done on it. This Jazz has a little bit of an issue passing emmisions, coz i have aftermarket catalytic convertor installed and more than 250k km on the odometer. Its pretty worn out, it will need some service in the summer