M103 Idle/Sputter/Stall Intermittent Issue
 

Morning all,

I've started driving my 93 190E (m103 3.0) to work and the past two days have had some interesting problems.

My daily commute is 65 miles one way, all highway pretty much.

Monday:
-No issues once so ever until I got off the turnpike. I took my exit ramp and found that the car had randomly stalled out. Looked down at my tachometer and it was at 0. I was able to pop it into neutral and get it started back up on the off ramp without having to pull off or anything. After that all was fine, drive home was too.

I did notice that the idle felt a bit rough. It felt, to me, that it get progressively more rough and then the engine controls would rev the engine up a bit and it felt better. It would rev up to about 850 RPM and then slowly drop down to 700 or something like that.

Tuesday, on the way to the office:
-No issues once so ever until I got into stop and go traffic and had to idle for a while. The idle felt rough as it did the day before. It was not horrible, not like a diesel. It felt like a miss.

Traffic started to pick up and I gave it some throttle. The miss feel got stronger and it felt like I was not running on all cylinders. At best I could do about 2K rpm and 40 MPH no matter how much I mashed the pedal. Luckily I was at my off ramp and getting off.

I sat through two red light cycles hoping that it wouldn't stall out. Then the engine did the rough idle, and rev up thing and it drove like nothing at all happened.

Tuesday, on the way home:
-Engine stalled on offramp from 77 to turnpike, I was able to re-start without issue. No other issues until I got off the turnpike.
-I was driving down route 5 and I down shifted, sending engine RPMs up to 3500-4000 and the engine backfired. Loud pop, tachometer dropped to 0, I up shifted, and then tachometer restored to normal.

Experimenting at Home
Naturally, I've not been able to re-produce any of the problems. I did put my meter into the diagnostic port and it was reading 19-25% duty cycle at idle. IIRC this means its running quite rich. I did have a new catalytic converter installed over the weekend. I wonder if lambda needs to be adjusted?

I just got to work and am still investigating and thinking about causes.

Any thoughts?

I can tell you that the plugs, rotor, cap, and wires were replaced all within the last 10K miles.

I did have some exhaust work done, a catalytic converter and new magnaflow rear muffler were installed.

The motor has about 120-125K on it, chassis has 247K



Edit: Added more..

Video:

https://www.youtube.com/watch?v=63jwApw05KA

My first thoughts are fuel starvation.

I had a vehicle that would not rev one time, had a crushed fuel line. Not saying THAT is your issue, but I would try to do a fuel pressure check under load and see what is going on.

Can easily rule out the CIS ECU by disconnecting it. Also worth checking out the O2 function.



Will it rev up in neutral?

I did not think to throw it in neutral and see. This problem isn't easily repeatable and seems random. My entire 1h journey home it didnt do this at all. I let it idle in my drive way for 30 minutes then went to take it to the shop...then it did it. I filmed it and that was about it. Not more than 20 seconds after that video did the motor perk back up and run normal

Firstly 3.0 and not a 2.6 in a W201?

(anyway)

Where's the oxygen sensor fitted on your car? => I'm thinking if it is close to the new cat you should check the wiring to make sure there hasn't been an unwanted modifcation

Try a new fuel pressure relay ,these shut down at any time , and it will stall your engine.It cuts of the 12 volt power to the fuel pump .. With mine i conected a bulb up to my pump + - and had the wire with a bulb fixed to the end ,it will stay lit up till relay stops .So if it goes out the pump would have lost its power ,due to faulty relay.

Yes sir, I transplanted a 3.0L m103 into the 190 back in 2009. Quite a fun upgrade.

A good point about the O2 sensor...

I had some exhaust work done over the weekend. A catalytic converter was new rear muffler was added.

The converter, I believe, is this, 608214 unit.
http://i.imgur.com/KZ38wDV.png

It looks like the O2 sensor is positioned after the converter...however my memory is recalling that in all the Mercedes O2 sensors I've changed (a whopping 3) that the O2 port was before the cat...

I dont know if thats a problem or not. I suspect it would not cause an intermittent issue though. Not sure.

In my car that would be the MAS relay:

Electronic Control Unit (ECU), Fuel Injection; MAS Control Unit; OE Rebuilt
Controls the fuel pump, RPM control, idle, A/C compressor, oxygen sensor, heater and onboard diagnostics.

Another interesting point. I might have another one sitting around here that I could rebuild and install. I've seen the work of the one rebuilding company..not so great.

My O2 sensor is fitted to the manifold but I know some of the earlier systems had a sensor in the first bit of the down pipe.

I'm just thinking if your sensor was not removed carefully during the replacement of the catalytic converter then the wires might have been stretched so now you have a loose / dodgy connection - pure guess work on my part. Just thinking along the lines of what has been changed recently and the areas in which the work has been done. Do you have a spare good O2 sensor?

I dont have one on hand. But I can buy one easily enough, they are only like $30-40.

Right now the car is up at my indy's. I should give him a call, see if he had any luck so far.

Error codes?
 

Does your 1993 have a similar DTC plug as my 1990 300E (same 3.0 engine). If so what codes are present? (This is the first place I look whenever I have an issue).

Next, I check the EHA to make sure it isn't leaking. While still in place, wipe it clean and place some talcum powder on it. Drive around for a few minutes and see if it's even slightly leaking. If it's not from the weep holes, then some new special EHA O-rings are needed.

Next, check the Crank Position Sensor. Unbolt it, clean it, re-install.

Next, remove and inspect the EZL for any even hairline defects, clean all the connections to it, re-install.

Next, get another OVP, then MAS (or fuel pump relay)

(BTW: the cruise control unit I got from you, still works like a champ- thanks)

Hi Benz Mondi!

When you say DTC plug, are your referring to the round plug on the driver's fender? I think its also called X11 port. If so, that was one of the first things I checked. It was reading, at op temp, at idle, floating between 19-25%. If memory serves fault codes are read out as solid percentages. I.E stuck at 50% would mean O2 sensor fault.

19-25% is pretty rich if I recall correctly.

I do also have this issue where the car, when cold, never wants to start up on the first time. It'll stall out immediately, second time it will start but run harsh until rpm's pick up. Then its fine.

Awesome news on the cruise! I'm glad to hear it! My 190's was one of first or second units I did, its still running! My 300D's has the most miles (of any that I know of) at 71K, still going strong!

Any news?

I had similar problems... twice... with my 88 300CE. First time eventually it would not restart & needed a tow. Dealer changed the FPR. About 3 years later started having the same problem. By then I had figured out to drop it into neutral restart and keep going. Took it to the dealer and told him about it. They checked & replaced ignition wires & rotor. Maybe plugs too, I can't recall from memory. Problem solved. That was five or six years ago. Never had a repeat. Knock on wood.

My two cents JD is do the simple & cheap things first. Wires & rotor are cheaper than the FPR.
Good luck. Losing propulsion is never good whether on the high seas or on the road.

I do have some news actually.

Shop wasn't able to reproduce the issues. This isn't a surprise, lol, machines never cooperate.

They pulled the cap and rotor off, didn't see anything obvious. They ARE fairly new.

They did find the 3-4 of the spark plug wires (at the plug end) were not all the way pushed onto the spark plug.

He did say that it appears to be idling smoother now. So I am HOPING that was the problem...time will tell.

I do intend on adjusting the lambda tower though, 19-25% is a bit rich. (right?)