Some new theories on my 606 problems - PeachParts Mercedes-Benz Forum

muleears · #1 01-13-2009, 06:00 PM

Some of you are familiar with my long saga of poor running and MAF codes on my 98 E300*. I spoke to a former mercedes tech who had the following suggestions, please tell me what you think:

1. Turbo is failing. Causes inconsistencies in air flow and trips the code, causes poor inconsistent power.

2. Timing chain stretch. Chain has stretched, consequently IP timing is off causing poor running, again tripping the MAF code.

3. Nothing wrong with MAF, electrical problem with them rare, thinks something else is tripping the MAF circuit code.

I'm keeping my theories to myself for now and waiting to see what you fellows and gals can come up with. I look forward to your comments.

*For some quick background: Car runs very bad, throws MAF code even after two new MAF's. Runs OK with MAF disconnected, but low on power.

#2 01-13-2009, 06:48 PM

Sounds like an EGR flow problem to me. Either a bad valve or solenoid.

muleears · #3 01-13-2009, 07:06 PM

Quote:

Originally Posted by ForcedInduction

Sounds like an EGR flow problem to me. Either a bad valve or solenoid.

Could be, I have gotten an EGR code once or twice also. Should I pull the intake/EGR and clean?

Matt L · #4 01-13-2009, 08:37 PM

I must note that your post count is now 667. That implies that your opening post in this thread was post 666.

I would think that your timing would have to be quite off for the computer to notice. Also turbochargers don't die that way; if it's failing so as to cause inconsistent airflow, you would almost certainly be chewing up the blades and burning a lot of oil.

I would check the EGR as well as the intake flaps.

Jeremy5848 · #5 01-13-2009, 08:50 PM

I agree that your next step should be to pull the IM and EGR and do a thorough housecleaning. While you are in there, make sure all o-rings, seals, hoses, etc. are in good condition and not old, cracked, leaking, etc. If that fixes the problem or at least helps, consider installing one of the EGR bypass techniques that have been worked out and posted here.

KarTek · #6 01-13-2009, 09:11 PM

My money is on:

1. Electrical system gremlins (most likely)

2. EGR/MAF interaction (almost as likely)

3. Bad ECU (highly unlikely)

That's all I can think of. It's going to take some tracing and verification of wiring pathways. Did you ever trace the MAF wiring using the guide I wrote up for you in the other thread?

Cervan · #7 01-14-2009, 03:57 AM

i think i know why your having trouble! if your tires are spinning all the time you never go anywhere XD.

Sounds like the egr is carboned up and stuck open.. allowing gasses to enter the intake all the time.

muleears · #8 01-14-2009, 04:11 PM

Quote:

Originally Posted by KarTek

My money is on:

1. Electrical system gremlins (most likely)

2. EGR/MAF interaction (almost as likely)

3. Bad ECU (highly unlikely)

That's all I can think of. It's going to take some tracing and verification of wiring pathways. Did you ever trace the MAF wiring using the guide I wrote up for you in the other thread?

I am horrible with electricity, I don't even know how to check continuity with my meter (no instructions) so I haven't checked the electrical stuff yet. I do know how to remove the intake though.

I don't know if I mentioned in the other thread, my youngest took it unexpectedly four wheeling and it is in the body shop. Should have it back this week.

Don't know if I'll get to the intake this weekend. It's supposed to be 15* here Saturday morning. I know for many of you that's not cold but for here it's freezing!

When I do it, should I use carb or brake cleaner on the EGR. Any parts I should NOT get cleaner on/in?

deltajetfixer · #9 01-14-2009, 07:32 PM

Quote:

Originally Posted by Matt L

I would check the EGR as well as the intake flaps.

Intake flaps? Hmmmmm...

muleears · #10 01-14-2009, 08:37 PM

I didn't think the turbo had resonance flaps, does it? I thought that was just the NA models.

deltajetfixer · #11 01-15-2009, 09:46 AM

Quote:

Originally Posted by muleears

I didn't think the turbo had resonance flaps, does it? I thought that was just the NA models.

Your thought is correct.

muleears · #12 01-15-2009, 09:59 AM

How about the other theories, the bad turbo and the stretched timeing chain?

KarTek · #13 01-15-2009, 10:28 AM

Quote:

Originally Posted by muleears

I am horrible with electricity, I don't even know how to check continuity with my meter (no instructions) so I haven't checked the electrical stuff yet. I do know how to remove the intake though.

Unfortunately, having some electrical knowledge is almost a prerequisite for many DIY jobs and diagnostics on the later 124 cars and up. I'm tempted to buy an ocilloscope or a waveform meter of some sort just to become more familiar with how the car operates.

To check continuity is a simple matter. First, set your meter to either the diode symbol (looks like an arrow meeting a sideways "T") or to one of the lower ranges in the Ohm (looks like an omega) settings - like 200.

Next, if your meter has leads that detach from the body of the instrument, make sure the black one is plugged into the "Com" port and the red one is plugged into the one that's marked with either the Ohm (omega) symbol or the diode symbol. There's lots of different types of meters so I'm just giving you general information that may or may not apply in your case.

If you're set up properly, touching the leads together should result in a 0.00 reading or something similar. You're basically looking for the reading to change from blank to a 0 when the leads are touched together. If you're using the diode setting, the meter may have a feature that emits a "beep" when the leads are touched together. This is handy but can by confusing bedause some partially connected circuits will cause the meter to emit a short beep. For the true continuous circuits, the beep will be steady and last as long as the circuit is complete.

You can play around with different settings on the meter and touch the prods together to observe what happens.

As to your other ideas, I believe the MAF code is causing the lack of power rather than the turbo. I can induce a MAF failure code on my car and it will run poorly (no boost, won't shift if the throttle is floored, just runs up to about 4500 RPM and hangs there) until the code resets itself. If you're curious about the turbo, you can certainly take the tapered intake hose of it, reach in and spin it with your fingers. It should spin freely without any scratchy feeling. Understand though, that it won't spin like a top - gradually slowing to a stop, because there's no oil pressure to support the bearings. For giggles, you can check the play. You may be able to detect a little side to side play (radial) which is OK but there should be no perceptable 'in and out" play (longitudinal).

I would pursue the EGR cleaning route as it is proven that an EGR malfunction can trip a MAF code. The inappropriate introduction of exhaust into the intake may also be causing the rough running.

muleears · #14 01-15-2009, 11:45 AM

Quote:

Originally Posted by KarTek

Unfortunately, having some electrical knowledge is almost a prerequisite for many DIY jobs and diagnostics on the later 124 cars and up. I'm tempted to buy an ocilloscope or a waveform meter of some sort just to become more familiar with how the car operates.

To check continuity is a simple matter. First, set your meter to either the diode symbol (looks like an arrow meeting a sideways "T") or to one of the lower ranges in the Ohm (looks like an omega) settings - like 200.

Next, if your meter has leads that detach from the body of the instrument, make sure the black one is plugged into the "Com" port and the red one is plugged into the one that's marked with either the Ohm (omega) symbol or the diode symbol. There's lots of different types of meters so I'm just giving you general information that may or may not apply in your case.

If you're set up properly, touching the leads together should result in a 0.00 reading or something similar. You're basically looking for the reading to change from blank to a 0 when the leads are touched together. If you're using the diode setting, the meter may have a feature that emits a "beep" when the leads are touched together. This is handy but can by confusing bedause some partially connected circuits will cause the meter to emit a short beep. For the true continuous circuits, the beep will be steady and last as long as the circuit is complete.

You can play around with different settings on the meter and touch the prods together to observe what happens.

I would pursue the EGR cleaning route as it is proven that an EGR malfunction can trip a MAF code. The inappropriate introduction of exhaust into the intake may also be causing the rough running.

Thanks Evan that was very helpful. After I get the meter set up I connect the leads to each end of the same wire and see what happens? I should get a "0" if the circuit is complete? And something else if its not?

I don't know if I'll attack the intake this weekend its going to be very cold.

Is there a solenoid on the EGR? or is it vacuum switched? I guess It would be vacuum since there is a vac. line to it...

Could the O ring at the EGR be leaking and causing this?

KarTek · #15 01-15-2009, 11:54 AM

When you play with the meter, note that the reading goes to 0.00 or something similar with the prods are touched together. You'll see the same change when you touch both ends of a continuous wire.

There is a vacuum modulator for the EGR - it's the one you swapped for the identical piece on the turbo wastegate. There are no other wires or sensors on it.

There are no O-rings on the EGR, just a V-band clamp on the exhaust manifold and one on the EGR which should both be snug.