W124 surging and dying. Please Help!!
 

Hello All, My 1986 300E has an intermittent problem. It hard starts cold but, that is just a minor inconvenience. The problem is it will "bog down" or lose power at all speeds. While driving, it suddenly loses power and starts to lose speed. I floor it and it will continue dropping like it is out of gas. Most of the time it will kick in and jerk the car while taching out (due to my foot). Sometimes it will die all together and coast to the side of the road. It then becomes a bugger to restart. I have changed the fuel pump and filter. The cap and rotor appear to be good. I have heard CPS, fuel relay, and temperature sensor. I don't want to throw more parts at the problem but I am frustrated. I love the car dearly. It is a hand me down and I just want it running well again. I have searched the Forum but nothing really fits. Help Please!! Thanks for any and all help!!

Chad

There are many things which could cause this situation, however, I had similar symptoms with my 86 300E. You stated the cap and rotor "appear to be good", well I thought mine was too and it was the rotor which was the culprit.

Why not take it to a MB professional mechanic? They have the testing equipment and the skills needed to determine the problem.

Steve

I am trying to do the work myself. I am fairly mechanical and cant afford to take it to the dealership. I have called around my area and none of the independents know much about them. Thanks.

Sounds like you are saying the engine is reving up to redline, but the car is not moving like it should. Is this correct?


I find it hard to believe that no one knows how to work on one of the most common Mercedes cars out there.

Start at the basics,check all wires for to high resistance,cap and rotor for corrosion,If you have not done a major tune up,do it now,this way you have eliminated a major group of problems.After all of this and you still have the problem, I would lean to wards the position sensor. but before you go into that do a fuel pressure test. If you have good fire and good pressure the next would be that pesky position sensor.JNT

Chad, you should share where you live. Someone maybe able to steer you to a MB shop.

Keep in mind that paying for skilled diagnosis at say $75.00 or even $100.00 an hour is inexpensive as compared to say replacing a fuel pump that wasn't bad in the first place.

Steve

After a reread I find you have done the fuel pump why did you start at that point? well as I said you are probably looking at a position sensor going out.JNT

I have a very similar problem to the one the original poster described, although my car doesn't die at highway speeds (yet). I have replaced the O2, vacuum hoses, cap, rotor, plugs and wires in attempts to fix the problem.

The pulsing that comes through tells me that the engine itself is just fine, as a pump, but that the management is having problems.