Well, after a good-nights' sleep, here's my current analyse:

- One of the components of the ME-Motronic system was starting to fail and the system software was "compensating" for the failing component;

- When I dis-connected the battery, all the stored "compensation data" was erased and the ECU was "reset";

- When the battery was re-connected and the engine re-started, now with default ECU values, the engine will not run because either the mixture control is way off OR the timing control is way off;

- What is the offending component ? I vote for, in order of probabilty ; Air Mass Sensor, Elec. Throttle Actuator, accelerator poteniometer, the ECU.

- My deduction : mixture control being way off caused by faulty AMS that was starting to fail since a few months and was compensated by the system itself.

Besides, it's "relativly cheap" and very easy to remplace.

Are they "repairable" or can they be "cleaned up" ?

THANKS A 1,000,000 guys !

 

Euh, the AMS "relativly cheap" comes to $350 ... before springing for the air mass sensor, is there anyway to test it to know that is is faulty ?

 

Just spoke to an ECU specialist in the UK : the Air Mass Sensor is easy to test : connect voltmeter to ground and the signal wire : at idle should read about 1V and on acceleration should jump to about 4V , since I can't accelrate just blow hard against AMS connected but pulled from housing should see jump to 2v - 3v means it is working.

Trid that and it is working. I'm now down to the ECU : it is the only device that is sensative to a "reset" when you dis-connect the battery, for example. I don't want to know how much they cost from MBZ....

 

while the engine is idling, disconnect it.

if the engine runs different, then it's working.

put it in gear, cruise at 20km/h and blip the throttle. bad sensor will make the engine cough and misfire on intake.

 

Thanks Sleepwalker - It appears that the Air Mass is NOT faulty > it's looking more and more like the ECU : let's face it, it's the ONLY componant that has "volatile memory" that would be affected by a battery dis-connect.

Now I need to find a way or someone to test the ECU : ANY IDEAS ON THAT ?

 

Have the ECU reflashed before you replace it. That is, have a shop reload the software as we discussed earlier. I know it would be money out the window if the ECU itself is shot, but you might save alot if it's not.

Maybe you can work a deal with a shop that would reload the software and apply that cost towards a replacement ECU if the reload didn't solve your problem. It's not like they have to labor for hours to reflash the ECU.

 

that air mass test is bollocks i am a qualified mercedes diagnostic technician and believe me it is the air mass sensor i work in a dealership and know my stuff. if you dont want to pay mercedes money for ams use the bosch number and order direct from them should save you 100ish. as for a fault code air mass usually doesnt store a fault with sensor unless it is open circuit or intake air temp sensor (within ams) has gone down usually you will get mixture adaptation fault and numerous cylinders misfiring we charge for a quick test 0.3 hours that is the book time op code 54101101 they cant charge more than that

 

OK mawls, I would tend to agree with you on this : no way my cheepo multimeter is going to give me a proper "profile" on what the AMS is putting out. I will say that I did get a fault code read-out from the Mercedes dealer some months ago and yes there where mis'-fire codes ( P0305 P0306 P0304) which , based on what you are saying, may be indicative of a failing AMS. Furthermore, I reckon that the system has been "adapting" to the failing system, which may just well be the AMS... I'm going to replace the AMS tomorrow. Film at 11 !!

 

Why doesn't M-B use "speed density" when the MAF fails? Is there is no backup for a MAF failure?

 

there is a substitute value.

the control unit will consider 30 degrees for intake temp for emergency running.

the injection time will be based on the opening of the throttle valve... but MwCH said it doesn't open or response to the pedal position at all