OM606 stalling after brakes applied - PeachParts Mercedes-Benz Forum

EdzBenz · #1 03-08-2013, 06:31 PM

Fellas,
I have a weird problem going on with my 606 turbo. Here's what's happening:
-Engine begins to die/stall when the brakes are applied. This stalling happens when the transmission is in park or drive and the brakes are applied. Slight pressure on the brake pedal makes the engine start to hickup. Full pressure on the pedal makes the engine completely cut out.
-Engine idles fine just sitting in park, no hickups
-No fuel leaks can be seen
-No air in the fuel lines can be seen

I am at a loss as to what could be causing this problem. Could this be something to do with the brake booster pulling too much vaccuum from the engine?

Any help is really appreciated.

Recent work done:
-Timing chain replaced
-Fuel lines replaced
-Oil change

Chris W. · #2 03-09-2013, 07:36 AM

Everything points to a vacuum issue. Not sure how excess vacuum would get to the line for the shutoff valve, but you could try pulling the line to the shutoff valve, plugging it, and see if you have the same problem. If so then what you suggest would seem to be the issue. Don't know how to fix, however.

Rgds,
Chris W.

'95 E300D, 389K

jay_bob · #3 03-09-2013, 07:40 AM

Bad check valve in vacuum system?

KarTek · #4 03-09-2013, 07:52 AM

These cars have no vacuum system to speak of. Main line runs from the pump to the booster for the brakes. It splits there and runs to the turbo wastegate, the EGR and to the interior of the car where it connects to the aux vacuum pump to run the door locks and HVAC.

Just to see if it does something, try disconnecting the main vacuum line at the pump and run the car with no vacuum. This is all I can think of, no theories just the crudest stages of troubleshooting.

jay_bob · #5 03-09-2013, 09:10 AM

Is this on the 99?

If so that car has electric fuel shutdown, not vacuum shutdown like the 124s and older.

That is a real head scratcher then...

JimSmith · #6 03-09-2013, 01:16 PM

Similar to what I am experiencing, however, on my 1998 the engine merely goes to idle and it happens when I use the blinkers. It disables or overrides the cruise control and then the input from the throttle pedal. Occasionally this happens when I am merely driving - I have to let off on the throttle to idle position, and then the throttle works fine. If I leave the blinker on, and keep my foot on the throttle, the engine will pulse with the blinker - idle during the blinker "on" cycle, resume normal engine response to the throttle position during the blinker "off" cycle. Very odd.

At the moment it is snowing and the car is outside so I am not inclined to dig into it. But, I have an after market trailer hitch installed, and note the driver's side brake light lights very dim, while triggering the "bulb out" alert on the dash panel. So, I presumed this is a problem where a short is telling the electronic throttle the brake is on, and that forces the engine throttle to the idle position.

Your problem sounds a bit more severe as my engine never shuts off - it merely defaults to the idle mode.

Jim

pawoSD · #7 03-09-2013, 01:32 PM

Sounds like an issue with the wiring harness or idle computer/actuator.

Jeremy5848 · #8 03-09-2013, 03:13 PM

I can suggest a cause based on what I know of my '96 E300, which should be very similar. The W210 electrical system includes a circuit that sends the engine back to idle whenever you apply the brakes. I discovered this when trying to drive two-footed -- every time I pressed on the brake I suddenly lost control of the engine and it went to idle. Didn't stall but I had no throttle control.

The two situations described in posts #1 and #6 are probably related to a malfunction of this electrical circuit. I agree with the comments that the problem may be unrelated to the vacuum system; I can't see the vacuum pump putting enough load on the engine to cause it to stall; there is no vacuum connection to the IP in these cars.

EGR uses vacuum -- I suppose there could be some kind of malfunction that would cause a flap to close and cut off the engine's breathing air, but that's pretty far out.

I think the environmental insulation problem had been sorted by 1998 but there could still be some problem in the wiring harnesses, caused by age or by the recent work, or both.

Question -- are any codes being thrown?

Jeremy

JimSmith · #9 03-09-2013, 11:55 PM

I have a primitive code reading tool and have checked, with no codes detected. I presume the brake light circuit is part of the trigger to drive the engine to idle, and my car's issues with the tail lights is sending an erroneous signal that triggers the safety feature that defaults the electronic throttle to idle. Something Toyota might want to check into.

Jim

pawoSD · #10 03-10-2013, 12:26 AM

How would it "send" the engine to idle? Pretty sure all engines "look/wait" for idle once no throttle is being applied, but may be at higher speeds due to the drive line coupling pressures keeping it moving faster/coasting if the car and transmission are moving fast enough

JimSmith · #11 03-10-2013, 12:56 AM

The throttle is operated electronically on this auto. So, there is no mechanical connection between the pedal and the injection pump.

There are a couple of sensors that have to be "seeing" a prescribed set of conditions to allow the pedal to control the throttle position on the injection pump. When one of the sensors, like the brake pedal position sensor, detects the brakes have been applied, the default position for the throttle is the idle position, and the electronic actuator drives the injection pump throttle to the idle position, nearly instantly. Under normal operating conditions there is no odd sensation, as typically one drives with the right foot either on the throttle or the brake, and removing one's foot from the throttle to depress the brake involves an expectation of a sensation of deceleration. So when that happens whether it is engine braking or brake system braking the effect is controlled by the driver's pressure on the brake pedal.

The sensation to the driver (me) when I am driving and I turn the blinker on to change lanes at highway speed, and the blinker operation is "read" by the brake position sensor circuit as having applied the brakes, is a sudden loss of power accompanied by engine braking and deceleration. When the blinker light circuit transitions to turn the blinker lamps off, the signal being misread disappears and the engine comes back to life, at the throttle position input from my right foot. Then, the blinker circuit turns the blinker lamp on and the engine dies again. A bit disconcerting, but I can deal with it.

Another event occurs with the tail lights on - intermittently the same issue as the blinker except there is no cycling due to the blinker circuit. In this case I have to lift my foot to allow the throttle input from the pedal "agree" with the idle position caused by a weak short in the rear lamp circuit affecting the brake position detection circuit, at which point I can use the throttle pedal unrestricted again. Very odd.

I will dig into this tomorrow if the snow here melts.

Jim

Jeremy5848 · #12 03-10-2013, 01:02 AM

Quote:

Originally Posted by pawoSD

How would it "send" the engine to idle? Pretty sure all engines "look/wait" for idle once no throttle is being applied, but may be at higher speeds due to the drive line coupling pressures keeping it moving faster/coasting if the car and transmission are moving fast enough

The 1996 and later diesels are "fly by wire," that is, there is no mechanical connection between the accelerator pedal and the diesel injection pump. Instead, the footfeed operates an electronic control connected through the EDS electronics to the IP. If while driving you press on the brake pedal, the brake switch sends a signal to the EDS electronics and the signal to the IP is turned off. The engine drops to idle speed regardless of where your foot is on the accelerator pedal. This is done as a safety measure. Somewhere in one of my books a description of this "feature" is hidden; at the moment I cannot find it.

Jeremy

EdzBenz · #13 03-11-2013, 04:57 PM

Fellas,
Thanks a ton for the replies. A few updates based upon your posts:
-No codes
-I forgot to disclose that the SOV o-ring was replaced while we did the fuel lines and timing chain. Maybe the vaccuum line on the SOV wasn't replaced properly?
-The SOV itself was NOT replaced. Maybe the SOV has failed or is acting up and needs to be replaced too?
-I replaced the wiring harness/ECU about 5 years ago. I feel that should still be good.

Thanks again. I really appreciate it. Any other feedback is certainly appreciated.

EdzBenz · #14 03-15-2013, 04:04 PM

Quote:

Originally Posted by Jeremy5848

The W210 electrical system includes a circuit that sends the engine back to idle whenever you apply the brakes.

The two situations described in posts #1 and #6 are probably related to a malfunction of this electrical circuit.

Could you tell me the location of this electrical circuit? I want to try to test it, or swap it out.