oil in fuel system

[oharab]

I've just replaced the rubber boot that goes from the air filter into the throttle and the pipes that go to the idle valve. Inside the throttle, where the big butterfly flappy thing is was a load of thick oil. There was also some at the air filter end.
Where has this come from? Is it normal? I'm wondering if it's come from the breather pipe.
I cleaned it out with some carb cleaner, do I need to do anything else? Can I use carb cleaner to clean the injection system? Does this have anything to do with the car idling at 1000 rpm sometimes? Not all the time, just most of the time.

Cheers

Ben

[oharab]

<cheeky little bump />

[uscharalph]

I've just replaced the rubber boot that goes from the air filter into the throttle and the pipes that go to the idle valve. Inside the throttle, where the big butterfly flappy thing is was a load of thick oil. There was also some at the air filter end.
Where has this come from? Is it normal? I'm wondering if it's come from the breather pipe.
I cleaned it out with some carb cleaner, do I need to do anything else? Can I use carb cleaner to clean the injection system? Does this have anything to do with the car idling at 1000 rpm sometimes? Not all the time, just most of the time.

Cheers

Ben

I've found just a little in the same area, but nothing like a load of thick oil. I also was waiting to see if you got any responce.

[Kalevera]

Ben, a car with significant blowby will throw lots of oil into the butterfly. Some is normal, it drains into the intake and is burned. Excessive should be dealt with accordingly and may point to other problems.

Residue is normal but should be cleaned (hence products such as the BG system -- my personal favorite, sea foam, and the like exist). I've found that an excessive amount of gunk around the throttle body can mess with the throttle position sensor, resulting in pendulum shifting on automatics and whacky idle and cruise.

Sorry to have missed your thread earlier.

best, whit

[Interceptor]

Ben, a car with significant blowby will throw lots of oil into the butterfly. Some is normal, it drains into the intake and is burned. Excessive should be dealt with accordingly and may point to other problems.

What is blowby?

[dacoyote]

What is blowby?

I would assume Whit is talking about...

BLOW-BY: Combustion gases, composed of water vapor and unburned fuel, that leak past the piston rings into the crankcase during normal engine operation. These gases are removed by the PCV system to prevent the buildup of harmful acids in the crankcase.

-Charles

[Interceptor]

BLOW-BY: Combustion gases, composed of water vapor and unburned fuel, that leak past the piston rings into the crankcase during normal engine operation. These gases are removed by the PCV system to prevent the buildup of harmful acids in the crankcase.

So, basically, if you have excessive blow-by, it's time for an engine overhaul?

[dacoyote]

So, basically, if you have excessive blow-by, it's time for an engine overhaul?

It's a sign of bad things.. Whit and the smarter people on the board can tell you more if it's something that has to be jumped on and what the levels are on the bmws...

-Charles

[632 Regal]

blowby is normal

excessive blowby is not

excessive blowby is a sign that either the rings are worn, not sealing from crap built up in the ring lands from dino oil, a worn cylinder bore, excessive fuel washing down the cylinders, or broken down oil and sometimes can be caused from bad valve guides (at least in detroit iron).

thats about the gist of things that I know.

[Kalevera]

Charles got the technical definition, but it's not necessarily a huge problem. M20 and M30 engines have the "PCV" built into the valve cover. I'm not knowledgeable or experienced enough to say whether the thing can fail; seems like a pretty simple design. I suspect that the biggest contributing factor to their demise (not to mention the demise of the engine) is bead blasting the valve cover. The plate is usually riveted in place, making it nearly impossible to remove the bead if it gets in there. Abrasive Sand + Engine = bad.

One point to remember is that BMW has consistently had problems with low quality gasoline. In the 80s, low grade stuff caused excessive carbon buildup, hence they developed the walnut valve cleaning machine. Then, they petitioned for better quality gas and got it. The engines still get gunked up over time and neglect.

We use the BG system at work and I have three anecdotes to share about it: 1) the other mechanic I work with ran it through his 325e, then inspected the intake to find it "brand new" clean, 2) Brett says that the M30 (ergo, the m20) has always been the best responding engine to the system, 3) I ran it through Fritz three weeks ago -- it smoothed out the idle and killed so much carbon that I had to adjust the valves back into spec; intake is much cleaner. Unlike seafoam, you effectively run the car on the BG for a few minutes (pull the fuel pump fuse, so no gas gets injected). The motor cadillacs on the stuff. Bill is probably still correct in that it messes with the ring lubrication and there are probably dispersion issues, but I need to rebuild my lower end anyway, so I had nothing to lose.


best, whit