[vonhuster]

Hello,

I have a '94 Mercedes 320e that just developed a new engine problem which I guess I would have to call an engine surge while at idle. It doesn't run properly at driving speeds either.

The engine had been running great with no misses and lots of power. However, it suddenly developed a problem where (when idling in park) where the revs constantly modulate between 5 and 15 krpm. When driving, the engine sputters and loses power if the gas pedal is pushed too quickly and past a certain point. If the pedal is pushed completely down while the sputtering occurs, it will continue to sputter for a couple of seconds and then take off with full power and run properly with even after the gas pedal is decreased.

I suspected (possibly) that the MAF might be the problem but it seems to idle the same with the MAF sensor disconnected. I guess that this could indicate either a completely bad MAF unit or a completely different problem.

The car has always had problems. I've addressed problems with the fuel pump relay and bad solder connections in the OVP. These problems have been corrected and the car had been running very well for several months.

Would anyone know where to start with this problem? My car doesn't have an obd2 and old error codes from previous problems are still loaded on the "code box". I plan on clearing those today and disconnecting the battery to reset my system for a fresh start.

I've been running for a week or so with the same gas in the tank with no problems. Still at the 1/2 full mark.

Thank you in advance for any help or suggestions. I appreciate your time and help.
Regards,
Tim

 

[sbaert]

First thing to check is to see if the vehicle still has its eco junk engine wiring harnesses and throttle body.

Check the manufacturing date on the throttle body itself and harnss behind the battery splash shield.

Anything made before 1998 is no good. These cars cannot be troubleshot if you still have the dreaded eco junk crap.

see link for more details

PeachPartsWiki: W124 Engine Wiring Harness Replacement

 

[vonhuster]

First thing to check is to see if the vehicle still has its eco junk engine wiring harnesses and throttle body.

Check the manufacturing date on the throttle body itself and harnss behind the battery splash shield.

Anything made before 1998 is no good. These cars cannot be troubleshot if you still have the dreaded eco junk crap.

see link for more details

PeachPartsWiki: W124 Engine Wiring Harness Replacement

Thank you for the advice and for the link. The link is very helpful. I do have the old (bad) harness. I'm sort of in a bind deciding if I should invest the money in a wiring harness (it would have to be a used one.) or hope that my problem is a real problem (meaning not a wiring harness short) that I can accurately troubleshoot and repair. I totally understand what you're saying, but I'm afraid that I would have much more than the value of the car invested if I bought a harness just to find out that I still need to buy some super-expensive part.

My car is getting close to 95,000 miles so I still have the dreaded head-gasket problem looming in my future.

Quite the quandary isn't it?

Thank you again. Your advice is great.
Regards, Tim

 

[humblejoe]

Tim, what side of pa are you in? I'm 45 Min west if Philly and have both early and late 104 harness, let me know if your close. I can help out. 95k is a baby, don't give up on her yet

 

[vonhuster]

Tim, what side of pa are you in? I'm 45 Min west if Philly and have both early and late 104 harness, let me know if your close. I can help out. 95k is a baby, don't give up on her yet

Thank you for the encouragement Humble Joe. It's been quite a ride with the e320. I still don't know which direction it's going with me. We've had several problems that we've made it through that seemed like they would be costly but turned out not to be. It certainty is a beautiful car that rides great. My kids love it. It's sort of a love hate relationship. The contrast between the incredible quality and workmanship shown in the car alongside of biodegradable wires, 90.000 mile head-gaskets, and costly, way over the top over-engineering amazes me and attracts me for some reason.

I live in Central PA about 30 miles south of State College. Thanks for your offer to help out. I just might drag you down though.

Thanks again. Regards, Tim

 

[vonhuster]

So I managed to reset the DTC box and clear everything out by disconnecting the battery for a while. I was hoping that something might also be reset with the computer, but no luck. The car still idles the same.

The DTC automatically came up with an error code of 10 which is an error of " voltage at hot wire mass air flow sensor too high/low" Which means that either
1.) the maf unit is bad.
2.) My wiring harness is shorted.
3.) Something else is wrong and the DTC box thinks that it's the
MAF unit.
4.) There's something else lurking that I'm unaware of.

Does anyone know of a surefire way to test the MAF with resistance or voltage tests? I can't seem to find the information that I'm looking for. All I know is that I have 14v at pin 2 which is the battery voltage with the engine running. I'm not sure if this is the correct voltage or not. It seems to me if this is the voltage used to measure the airflow it should be a smaller, set, regulated voltage and not a varied alternator voltage.

Thanks in advance.
Tim

 

[sbaert]

95K is barely broken in. As I said before, real diagnosis is futile with the original eco crap wiring in place. Ignoring eco junk usually leads to reliability issues and ECM damage.

Also, resoldering OVP and other relays is a band aid solution. The OVP, in particular, is a wear and tear item. Replace it, using brand new OE MB or KAE(hler) brand relays, with every new battery install and you'll never have a OVP problem.

 

[plinker17722]

vanhuster .You might have a faulty ETA .Your throttle is electronic [ Electronic Throttle Actuator ] for a little information on your problem check this out on YouYube videos . It might help you to find the problem and undrstand mote about how the ETA works .
Just put this in you tube search box - Mercedes M104 ETA Throttle Body Bad Wiring Symtoms You will find lots of information in there .Good luck in fixing it .

 

[vonhuster]

Thank you all for even more suggestions and helpful links.

So, after assuming for over a year that I had the old wiring harness with the "Eco-junk" wiring, I found out today that I do not. It turns out that my harness was manufactured in 2012 and the wire that made me assume that I had a bad harness (coming from the bottom of the ecm) was only a jumper that with only an inch of defective wire. I've looked at that defective wire several times and thought that it was connected to my wire harness.



I guess this brings me back to square one....I was wondering if anyone could tell me if my e320 should run the same at idle with the MAF sensor disconnected? Mine doesn't seem to change even a little. I'm sure hoping that the problem is the MAF and not the throttle as suggested. It seems like it's a wiring mess too. I wasn't aware of that problem.

Thanks again.
Regards,
Tim

 

[sbaert]

Your symptoms do not fit those of a bad MAF, but do fit those of a bad throttle body . . . . perfectly.

 

[vonhuster]

Your symptoms do not fit those of a bad MAF, but do fit those of a bad throttle body . . . . perfectly.

Not good news sbaert. Thank you none the less.


Is thre a sure fire way to know for certain that the throttle body is the culprit? I've been looking at the plans for making a test fixture for the error code module. I don't know if this method is reliable or not.

 

[vonhuster]

vanhuster .You might have a faulty ETA .Your throttle is electronic [ Electronic Throttle Actuator ] for a little information on your problem check this out on YouYube videos . It might help you to find the problem and undrstand mote about how the ETA works .
Just put this in you tube search box - Mercedes M104 ETA Throttle Body Bad Wiring Symtoms You will find lots of information in there .Good luck in fixing it .

Thank you Trevor.

The help on this forum astounds me. I greatly appreciate it.

 

[sbaert]

Check the build date code tag on the throttle body. The tag is visible in the middle of in the manifold with a decent flashlight.

The date code should look like xxMxx such as 94M08 indicating a unit made in August 1994.

Anything made before 1998 is eco junk.

 

[DrewHolden]

Tim, I had a similar problem recently. It was my ETA. I had suspected that was the case when I saw the date code was from April 1992. The wires inside mine were so toast, just crumbling off. Surprising it even ran. Put a new ETA in and it's been great since. Although it was costly, I don't regret it. Good luck!

 

[plinker17722]

If you can get a check done on it before you go spending $$$ on it . Just dont go off earsay .. The wires in loom that goes to it can cause problems,, so do a check on this also .

 

[vonhuster]

Check the build date code tag on the throttle body. The tag is visible in the middle of in the manifold with a decent flashlight.

The date code should look like xxMxx such as 94M08 indicating a unit made in August 1994.

Anything made before 1998 is eco junk.

Thank you for the advice sbaert. I checked the tag.... the throttle is a '93 vintage. The car is a '94.

Tim, I had a similar problem recently. It was my ETA. I had suspected that was the case when I saw the date code was from April 1992. The wires inside mine were so toast, just crumbling off. Surprising it even ran. Put a new ETA in and it's been great since. Although it was costly, I don't regret it. Good luck!

Thank you Drew.

My throttle is a '93 and it's looking very much like this going to be the problem. Did you do anything to verify as an absolute certainty that this was the problem before replacing?

]

If you can get a check done on it before you go spending $$$ on it . Just dont go off earsay .. The wires in loom that goes to it can cause problems,, so do a check on this also .

Very good advice Trevor. This is my major hold up. I don't live close to any mechanic that i would trust to diagnose the car. The closest (not very close at all) is very expensive and has a bed rep. They have already given me bad diagnoses and repairs in the past and are the main reason that I try to do as much repair work as I can myself.

My main question now is how to diagnose (for certain) that the throttle actuator is the problem.

 

[vonhuster]

Thank you all for the great replies since I last logged in. I've responded to the replies in the post directly below this one.

I was wondering if anyone could tell me how to properly diagnose the throttle body with certainty? I'm thinking the homemade test fixture for the Diagnostic test codes might be the answer. Is this true?

I'm also hung up on the MAF as it seems to be the only source of any error code. I am aware that all symptoms point to the throttle body. I'd just like to get this out of the way. The engine runs exactly the same with the MAF connected or disconnected....is this normal?


The throttle actuator seems to be a costly investment. I'd like to avoid any any mistakes if possible.

 

[sbaert]

...
My main question now is how to diagnose (for certain) that the throttle actuator is the problem.

That is the crux of the problem. These late model cars all came with eco junk wiring and until you get rid of it, you can't diagnose it reliably.

BUT, based on your symptoms AND the build date my money is on the throttle body.

Easy DIY job. But make sure you install a new throttle body gasket whenever you swap the unit.

You can find post eco junk era throttle bodies on eBay every day of the year for not too much money. Just make sure the p/n#s are identical since you cannot install a ASR throttle body in a non-ASR car or vice versa.

 

[vonhuster]

Digging up this old post to give an update......I had some good news to report and decided to wait until I knew that it was permanent. I lost track of time and then kept forgetting to update. I (of course) have another question to ask and had to change my forgotten password so that I could log on again. Sounds totally ungrateful, but I really am not.

The good news is that my car suddenly started working properly and hasn't surged since. I really do appreciate this forum and all of it's members who are so helpful.

I apologize to anyone reading this thread who is hoping for an answer to their similar problem....I have no answer for why my car suddenly started working properly. It just did.

Sorry for the delay.
Thank you all for your awesome help.

Regards,
Tim