1993 300E running poorly - the saga continues - Benzworld.org

GDC · 10-23-2007, 10:02 AM

Hello all

I am looking for help in chasing down a misfire at all speeds, in gear or out. My car is a 1993 300E 3.2l M104 with the Bosch HFM DIS system.

When I bought the car in April with 119,K miles, it ran rock solid and had all of the paper work showing maintainence up to 98,000 miles. I did the 120K service and all was well until August when it started to have a bad idle surge.

I replaced the OVP and then chased this surge with help from this forum to a bad wiring harness which I rebuilt. I then found that the throttle actuator wiring was bad as well so I rewired it, again with help from this forum. I then found that the voltage regulator was bad, so I replaced it and the car ran beautifully for the last week with just a very slight miss at idle.

All of a sudden, it developed a really nasty miss, it felt like it was losing at least on cylinder, maybe 2. I changed the plugs and wires, pulled the fuel rail and replaced the injector o rings, but the problem is still there. It seems to be the same cylinder, and at first I thought maybe a vacuum leak, but it doesn't change at all with any change in throttle, you can still feel it at highway speeds. I thought bad coil, so I swapped them around but this didn't cause any change and the fact that it has it at idle is leading me away from that cause, unless it is possible for one of the two outputs on the coil to fail while the other output continues to function.

I am thinking maybe a bad injector or camshaft position sensor. This is the first fuel injected auto that I have worked on so I really have no idea where to start. Could the camshaft position sensor cause this behavior? Could any of the emission control stuff cause this?

Here is a list of what I have replaced / repaired so far:

OVP relay
Voltage Regulator
Rebuilt Wiring Harness
Rewired Throttle Actuator
Cleaned and Swapped out MAF sensor
Cleaned Throttle Actuator
Replaced Injector O rings
Replaced Plug wires
Replaced Plugs

Thanks
Greg

GDC · 10-24-2007, 07:43 AM

Last night, the problem disappeared completely for about 20 minutes and then came back, but not as bad as before. Ignorance being what it is, I am becoming convinced that the problem is injector related. Can these injectors be rebuilt? Is there any way to clean them other than by running cleaner through the fuel? Any suggestions on testing them? Any advise at all would be appreciated.

Greg

deanyel · 10-24-2007, 08:42 AM

Are you reading the fault codes? Injectors can be rebuilt, and/or tested, at places such as this:

Cruzin Performance

GDC · 10-24-2007, 09:20 AM

I can't seem to pull any codes. I have built the reader twice now and the only time I get any light on this car is when the button is pushed. I was told by another user on this thread to forget the code reader, so I am sort of running ,if not blind, with very poor eyesight.

deanyel · 10-24-2007, 09:36 AM

Not sure why anyone would want to forget the fault codes unless they thought it was just more fun to struggle and throw parts and money at the problem. The built in LED code reader doesn't really tell you much - you need to build the code reader and read all the relevant pins. There is very likely a clue there. You have a private message.

GDC · 10-24-2007, 01:27 PM

This car doesn't have the on board reader. So my only option was to use the LEDtool which does not work on this car. The ones I have built work fine on my 1994, but I get nothing on this 93.

Greg