What controls idle speed on om606? - Page 2 - PeachParts Mercedes-Benz Forum

pimpernell · #16 09-01-2008, 02:58 PM

This information was provided in another thread, and may be helpful to you:

Jeremy
I took a defunct TPS apart. The TPS is actually a dual Hall effect sensor embedded in some rotating magnets. Aside from the shaft mounted magnets there are no moving parts. The hall effect sensors send out two 180 degree out of phase signals indicating throttle position. The ECU checks one signal against the other to validate the position of the throttle. Breaking any wire or shorting to any other wire in the bundle messes up the phase and invalidates the signal. This vastly decreases the likelihood of an accidental full throttle signal. Given the simplicity of the TPS, I'd suspect the connector or local wiring before suspecting the sensor.

Jeremy5848 · #17 09-01-2008, 03:11 PM

Pimpernell, from what year/model did you get this TPS? According to my DVD-ROM copy of the W210-series FSM, the TPS contains a potentiometer and an SPDT switch. No sign of any Hall effect sensors. I looked at the electrical schematics for both the '96 E300D and the '98 Turbo.

Jeremy

Jeremy5848 · #18 09-01-2008, 03:26 PM

Quote:

Originally Posted by Number_Cruncher

>>brake action over-rides the signal from the TPS telling the engine to cut down to idle.

Yes, dropping to idle is correct behaviour when the brake is pressed. This function itself can be over-ridden by pressing the throttle again - i.e., it only cancels the first application of throttle.

I went out to a parking lot and did some tests with my '96. The action is as you and nhdoc say. When you apply the brake, the engine goes to idle even though you may still have your foot on the accelerator. Additionally, my ScanGauge continues to display a non-zero number for TPS, e.g., 20 or 30 or whatever, suggesting that the ECU is still reading the throttle position sensor but is ignoring it as long as the brake is applied.

It also turns out that, with the car stopped (one foot on the accelerator and the other foot on the brake), you can gently and slowly press on the accelerator and the engine speed does not increase. If you "sneak up" on it, you can floor the accelerator -- get TPS all the way to 99 and the car does not move -- until you let up on the brake, then watch out.

On the other hand, if you rapidly move the throttle from a "low" setting to a "high" setting, the computer sees the change (perhaps it differentiates the TPS signal) and tells the FI pump to "go," even though you still have your foot on the brake.

So, I don't think I have a TPS problem after all -- it's just my tendency to drive two-footed around town. I shall have to be more careful.

Jeremy

pimpernell · #19 09-01-2008, 06:02 PM

Quote:

Originally Posted by Jeremy5848

Pimpernell, from what year/model did you get this TPS? According to my DVD-ROM copy of the W210-series FSM, the TPS contains a potentiometer and an SPDT switch. No sign of any Hall effect sensors. I looked at the electrical schematics for both the '96 E300D and the '98 Turbo.

Jeremy

It came from a thread pertaining to a 96E300d, that I believe you started regarding another issue you were having. In message 23, you will find the information I provided. If it was not accurate, I apologize for providing it.

OM606 NA breather plumbing question

Jeremy5848 · #20 09-01-2008, 06:40 PM

Quote:

Originally Posted by pimpernell

It came from a thread pertaining to a 96E300d, that I believe you started regarding another issue you were having. In message 23, you will find the information I provided. If it was not accurate, I apologize for providing it.

OM606 NA breather plumbing question

Yes, understand, but where did you get the TPS that you took apart? What year/model did it come out of? Mercedes might have gone to the more sophisticated design that you found in later models than my '96.

KarTek · #21 09-01-2008, 08:50 PM

Quote:

Originally Posted by Jeremy5848

Yes, there is an SPDT switch as part of the TPS. Here is the schematic.

Parrot, if you figure out how to take the TPS apart without damaging it, let me know as I'd like to take mine apart to check the switch. In my TPS, the resistance across pins 3 and 4 does not go all the way to zero when the switch closes. The minimum I read is about 200 ohms and the opening of the switch as TPS goes above idle seems to be flaky -- the resistance bounces around before going to infinity.

Possible dirty contacts? This problem may be related to my problem where the engine occasionally does not respond to the accelerator pedal at very low speeds (parking lot or stop-and-go driving). Since this is an "occasional" problem, I'd rather not wreck this $500 part taking it apart.

Jeremy

Jeremy,

Where did you get that diagram? I desparately need such a diagram of the injection control. I need the pin outs of all the lines going to the injection pump.

The circuit looks like what's on my truck. The switch is what Ford calls an "IVS" or Idle Validation Switch. It gives the computer a clear signal that the throttle is released regardless of the throttle position.

Jeremy5848 · #22 09-01-2008, 10:16 PM

Quote:

Originally Posted by KarTek

Jeremy,

Where did you get that diagram? I desparately need such a diagram of the injection control. I need the pin outs of all the lines going to the injection pump. . .

The diagram is from the DVD-ROM of the FSM for W210 cars. I assume you want the diagram for your '99? Let me look.

[Looking . . . ]

OK, the diagram is part of the Electrical Testing Manual, which is on-line, reached through a link in the DVD, and called "Web ETM Model 210." It is a huge diagram that runs in Autodesk WHIP. I suspect the only way to get at it is to have the DVD.

Under "Engine -- Fuel management," it is called "07.12-U-2000H / Diesel injection system with in-line pump (IFI) and electronic control / ENGINE 606 as of 09/01/97 up to 05/31/99 in MODEL 210" In addition to the schematic diagram, there is another huge page that has a legend for the diagram, a page of diagnostics, a page of connectors, and a page that lets you find each part in the engine bay. All of that is just for the injection pump. I don't know how to make copies that I can save in either jpg or pdf format and post here or in my Photobucket account.

I'm also concerned that there seem to be errors in the Web ETM. The diagram that is supposed to show the '98-99 model (turbo) engine actually shows the '96-97 NA engine.

Jeremy

KarTek · #23 09-01-2008, 10:26 PM

Actually, the '98 but you know what I mean... I'm trying to learn the control structure of the injection pump.

Jeremy5848 · #24 09-01-2008, 11:00 PM

See edit of my post #22.

KarTek · #25 09-02-2008, 05:13 AM

Thanks for looking into that. If you send me an email address via PM, I'll send you a .zip of a program like P-shop that will let you capture anything you have on the screen and save it as a picture file. Very handy...

nhdoc · #26 09-02-2008, 06:22 AM

Quote:

Originally Posted by KarTek

Thanks for looking into that. If you send me an email address via PM, I'll send you a .zip of a program like P-shop that will let you capture anything you have on the screen and save it as a picture file. Very handy...

In a pinch you can always hit your "print screen" button then open up microsoft's "paint" program and paste in the screen, edit it and save it to a jpg.