unintended acceleration! Kinda urgent - PeachParts Mercedes-Benz Forum

psaboic · #1 04-21-2016, 11:29 AM

Need some help.

On the way to work today, about 15 or so minutes into the drive, I noticed the car suddenly being VERY sensitive to the accelerator pedal. If I was going above 50 mph (about 2500 RPM according to the tach) I could feel it trying to accelerate on its own. Letting off the pedal and lightly applying the brakes brought it under 50 and it acted normal.

A few minutes later it started doing it again, but a little stronger. I slowed down to a stop and put it in neutral and it instantly revved up to about 5 grand. I shut it right off with the key and it shut off fine, but there was a cloud of black smoke in the air.

I waited about 30 seconds and started it up and idled fine so I drove away. All was fine until about 10 miles down the road when it started doing it again, but this time it was lightly pinging and I saw blue smoke out the rear window. I applied the brakes, brought it under 50 again and it was fine the remaining 10 miles of my drive.

I got to work, and popped the hood. the whole front side of the engine, the firewall, and the IP and linkage are covered in motor oil, as well as the injectors and lines. I just replaced my valve cover gasket and I think that is the cause of all the oil as it is simply not sealing well at all. But could that cause it to try to runaway?

I'll check the oil level in about 4 hours to see where it is at, but could a leaking gasket and oil spray cause my sudden acceleration issue? The car is a 83 300D turbo, and since the shutoff valve and brakes work fine, I think my vacuum pump is ok.

Gotta drive it home today so any ideas are appreciated.

Glenn

jt20 · #2 04-21-2016, 11:34 AM

throttle linkages

return spring on IP at the rear

"idle set" screw

lots of oil entering turbo

lots of oil passing the bearings in the turbo (blown turbo "seals")

oil return check valve on the air/oil separator drain

Stretch · #3 04-21-2016, 11:37 AM

Mat under accelerator pedal (!)

SD Blue · #4 04-21-2016, 11:40 AM

I fail to see how a leaking valve cover gasket could have spread that much oil. What was the oil level when you checked it?

psaboic · #5 04-21-2016, 12:07 PM

Well, the oil level was just a hair above the top notch on the dipstick right after an oil change (about 250 miles ago) The motor is still pretty warm right now as I just shut it off about an hour ago, but checking the oil it is about a 1/4" below the top notch on the dipstick. I have had an oil leak almost as bad one time when I changed a valve cover gasket, so I'm not overly surprised. The car was fine and not leaking any oil topside before I adjusted the valves and changed the cover gasket.

A friend from work just spoke to me and said she was following me the last 5 miles to work and at a constant 55 she said she could see a faint but steady trail of black smoke out of the exhaust pipe.

BTW, no floor mats in the car right now.

When I said covered in oil, it is not heavy coverage, just a what you would get if say you poured about a half a cup into the wind from a fan....Blows it everywhere if you know what I mean. The Valve cover gasket is definitely leaking, all on the drivers side, especially on the front corner and by the first two injectors. The back side and passenger side are dry.

Maxbumpo · #6 04-21-2016, 12:09 PM

Quote:

Originally Posted by psaboic

could a leaking gasket and oil spray cause my sudden acceleration issue?

Glenn,

Yes, oil will burn like fuel if there is a route for it to get into the intake manifold. If you still have the factory intake, I don't think that could happen.

jt20 · #7 04-21-2016, 12:12 PM

Dipstick tube happens to be in that area

psaboic · #8 04-21-2016, 12:41 PM

The motor is completely stock (air cleaner, piping, etc......)

The leak is definitely coming from the valve cover gasket. On my lunch break I will check the oil level and start it and see how it idles.

Could an oil mist get sucked into the air cleaner and burned???

Ceristimo · #9 04-21-2016, 12:47 PM

I'd remove the U-tube from air cleaner to turbo and take a peek to see what that looks like.
A small amount of oil coating the tube or a tiny pooled amount at the bottom is not unheard of, but if it's excessive, that could mean your engine is sucking up it's own engine oil through the turbo; that can create a run-away diesel.

As a side note: I put the valve cover gasket back wrong on my engine a few days ago, and even though that created a HUGE leak at the back of the engine (lost half a quart of oil in 30 miles...), oil did not get splattered around the engine bay... There is no pressure under the valve cover, so are you sure that spray-mist of oil is coming from there?...

SD Blue · #10 04-21-2016, 12:51 PM

Possibly a turbo seal starting to go?

Those that have reported turbo seal failure, mention that it starts as noticeable exhaust color with rapid loss of oil. Also, if this is the case, it may be hard to notice at idle.

babymog · #11 04-21-2016, 12:55 PM

It appears that you have checked your oil, if fuel gets into the oil and overfills it you will have a runaway, more at higher RPM than lower at first as the oil is churned up by the crank more / more windage.

If it does start to run away, do not pop it in neutral or you'll likely stand and watch the engine rev itself to death. If you can get the car to a stop in drive and shut off the key you have a better chance (not always).

leathermang · #12 04-21-2016, 01:08 PM

The oil level on any car should never ever be above the stated maximum...
as that leaves the possibility of foaming the oil...
which reduces the lubrication life of the oil really really fast....

psaboic · #13 04-21-2016, 01:12 PM

I'll definitely check the U-tube from the air cleaner. Probably Saturday will be the first chance I get to look at it in depth. As for the VC gasket. Yes, it is definitely leaking by the front drivers side corner of the engine and most of the drivers side of the gasket. I think the oil sprayed all around is from oil dripping from the leaking gasket, down the side of the block by the injectors, and then getting blown around from the wind in the engine bay at speed (coming from the bottom of the engine bay and possibly from the fan.) Doesn't take a lot of oil blowing around to put a coat of it on things....

psaboic · #14 04-21-2016, 01:15 PM

Quote:

Originally Posted by Ceristimo

I'd remove the U-tube from air cleaner to turbo and take a peek to see what that looks like.
A small amount of oil coating the tube or a tiny pooled amount at the bottom is not unheard of, but if it's excessive, that could mean your engine is sucking up it's own engine oil through the turbo; that can create a run-away diesel.

As a side note: I put the valve cover gasket back wrong on my engine a few days ago, and even though that created a HUGE leak at the back of the engine (lost half a quart of oil in 30 miles...), oil did not get splattered around the engine bay... There is no pressure under the valve cover, so are you sure that spray-mist of oil is coming from there?...

The main difference I see here is that your oil leak was at the back of the engine, mine is at the front, so it can then get blown back and all over the engine.

psaboic · #15 04-21-2016, 11:58 PM

Ok, I drove the car 39 miles home from work tonight with no issues. Granted I took it easy and never went over 2500 or so RPM. Took it apart and here is what I found.

1. The valve cover gasket has a small tear in it at the corner contributing to the leak, and the drivers side fron bolt was barely finger tight (must have loosened due to vibration).

2. The U-tube from the turbo to the air cleaner had about a tablespoon or so worth of oil pooled in the low spots, and of course had a fine sheen of oil over all of the inside. The turbo outlet itself had a few drops but nothing major, and the air cleaner had maybe a thimble full of oil in it. The last time I had the tube off was about 20K or so ago so the oil may have built up over that time.

My plan is to put it all together and run it for a couple of days and then pull the U-tube off again and see what I have. If it is full of oil or it unintentionally accelerates again, I'll see about getting the turbo rebuilt.

Based I what I have reported, do you think this is a sound plan, and do you think the turbo may be the culprit?

Glenn