[tim687]

Cmashaft sensors have been installed, radiator is installed and the engine idles happily

When driving however, I get a lot of faults in the fault counter. Sparkplugs are dirty, black and wet.

I can clean them, but I already did around 6k kms ago.

I think now is the time to stop oil consumption.

I've done a leakdown test and every cylinder is healthy.

 

[Deplore]

Oil consumption.... Hard to say. It's usually pcv, or piston rings, or valve stems.

 

[tim687]

There is a lot of oil in the black tubes connecting the throttle body to the intake manifold, so I don't think it's the rings.

I've replaced the main culprit of this engine however (front right engine cover), so I'm not sure what's causing the leak

@Kraut56 as you are a M137 owner yourself, how are your intake tubes?
Have you dealt with this problem?

 

[tim687]

There is also alot of oil on the sparkplug threads. I've replaced the valve cover gaskets, so I think that it could be coming from the PCV tubing.

 

[Deplore]

Do you by any chance have a lot of blowby?

 

[tim687]

I do have a little, not sure what is normal for an 22 year old engine. When I undo the oil filler cap and start her up (cold), she bounces very briefly.
It's not like vapors are spewing out of the filler hole when the cap is removed, but there is no vacuum on the crankcase either.

I haven't got much experience with blow-by, but I don't think that this is a lot of blow-by.

 

[tim687]

It seems like I do have a little blow-by.
It is nothing in comparison to this video.
Nothing is puffing out and I don't have the "freight train" noises coming out of the engine, but the filler cap dances briefly when I get on the throttle a little.

I don't think it's something concerning to be honest

 

[Deplore]

I'm not saying you should have zero blowby, all engines have some measure of blowby depending on design of PCV. Most BMW's and VW have negative crankcase pressure, in other words the PCV in those cars are designed to have a very aggressive vacuum. MB's haven't gotten to that level, and old MB did not have negative crankcase pressure.

So some measure of blowby is fine, and start up rattling of the cap is nothing to worry about. Now, if you had OM606 level blowby, then that's something different.

How does your car fare compared to this guy?

 

[tim687]

MB's haven't gotten to that level, and old MB did not have negative crankcase pressure.

I was actually comparing the amount of negative pressure in the crankcase to a friend's car. Now I know that this is normal. Thanks!

I'll do the bouncy oil filler cap load test when cold and when hot today and report back!

 

[tim687]

So, the video is showing more blowby than I have.
Which is excellent news!

Question still remains, what is causing the oil burn

 

[tim687]

My 'blowby' is by far not equal to this guy (watch at 29 seconds)

 

[Deplore]

Oil burn is a few things: PCV, valve stems leaking, piston rings. That's pretty much it, not a lot of sources.

 

[tim687]

So how can I identify one or another? I just needed to fill her up with 1.5L's of oil this morning.
The strange thing is, when I measure the oil level through the ICM before cold starting it shows OK, when I drive 5 minutes and try again after 5 minutes, it shows Add xxL of oil (which is correct as confirmed by my dipstick).

Why is this? I'd like to know the oil level before a cold start

 

[Deplore]

When the engine is cold, all the oil have pooled into the oil pan and raise the level. When hot, oil is flung around and is saturating at the top end. It's also sticky, so it's not like water where it will immediately pool in the oil pan again when you turn off engine.

You do the oil measurement with the oil hot, because that's the normal oil level will be when the engine is running. So if oil level was low by 1.5 when hot, then it really is low by 1.5l.

It's hard to say where the oil leak is coming from. I doubt it's the piston ring, as you'd have some decent amount of blowby if that was the case. Leakdown test would fail (15+).

Valve stems is more likely, or PCV is stuck open. But you replaced PCV before.

Do you have any leaks? Rear main seal and front oil filter housing is a known issue.

 

[tim687]

I do not have a valve in the PCV system, it's open all the time. One thing I did notice is that when the PCV hose is disconnected, it tends to smoke a lot less when cold starting.
I also read that if the piston rings are bad, that the engine should continuously smoke, not just during startup.

Well the bottom of the engine is not dry for sure. Although I doubt if it's the oil filler housing, because that is dry.

Please keep in mind that the threads of the sprakplugs where oily too. Could that leak into the cylinders?

 

[Deplore]

No, because if the oil is wicking past the spark plugs, you have far bigger problems than just a oil consumption.

 

[tim687]

Replaced the crankshaft sensor and the dat is still droning and misfiring at cold start.

When you drive it longer it seems to disappear.
I haven't had time to connect DAS since the transmission shifter linkage came lose.

Could it be that the replacement timing chain tensioner causes all sorts off issues, I'd assume that it would have skipped timing if it should, which should have caused other problems

 

[tim687]

The car stalled too when I tried to keep the revs up, seems to be the exact symptoms of a low fuel rail pressure.

Will try to do a measurement of the fuel rail pressure tomorrow.

The MAF air intake reading seems to be a bit on the high side at 32kg/h, which is just outside of the expected range

 

[Deplore]

Could it be that the replacement timing chain tensioner causes all sorts off issues, I'd assume that it would have skipped timing if it should, which should have caused other problems

No, because if chain tensioner was bad you'd have a lot more symptoms, not the lease is rattling noise at start up, chain slap and other whatnot.

You may have clogged cats which can cause misfires, and the fact that you had to disable the O2 sensor to get the car to run smoothly points to that.

Of course, fuel pump not pumping is another issue.

 

[tim687]

No, because if chain tensioner was bad you'd have a lot more symptoms, not the lease is rattling noise at start up, chain slap and other whatnot.

Pfew

You may have clogged cats which can cause misfires, and the fact that you had to disable the O2 sensor to get the car to run smoothly points to that.

Just letting the human mind do it's thing here. I do have a hissing noise when running, could this be increased exhaust backpressure that is escaping through the oxygen sensors?

DAS indeed pointed to the cats of the left bank not really working as they should. And the bank that is misfiring the most is the left bank.

So let's assume that I've replaced the cats, how could I prevent the engine from destroying another pair?