M103 stalls when OVP removed - PeachParts Mercedes-Benz Forum

Heep · #1 11-06-2010, 02:54 PM

Hi all, first tech post here, the first of many, I suspect!

Bought an '89 300E for $600 to tinker with (yeah, I know, the cheap ones are usually the more expensive ones, etc., but I was also looking for something with which to get my hands dirty). Has a multitude of issues but I'm going to try to tackle them one at a time. Anyways, I've spent the last two weeks searching and reading on this site and others and I feel I've adequately begun the education process!

The first issue that I'm tackling is a rough idle and severe hesitation upon application of throttle from low rpms. I'm starting to suspect a vacuum leak - the "economy" gauge sits at about 1/2 while idling. I tried to follow the peachparts diy "isolating vacuum leaks on a M103," but when I pull the OVP relay, the engine will not stay running unless I'm applying throttle, so I cannot proceed. Could a severe vacuum leak also cause the car to stall when the OVP is removed?

Thanks,
Mark

sptt · #2 11-06-2010, 11:27 PM

With the OVP removed, my car ran very rough and it was in "OK" shape. So, if you have vacuum issues, it might be pretty tough for car to stay on. The biggest issue of idle problems based on what I've read and seen in both my 103 and my daughter's are the hoses on the ICAV (Idle Control Air Valve). Do a search on it. if you take off the air cleaner assembly, you'll see it underneath facing the front. There is one hose going to the fuel distributer and one to the engine block. Once I replaced the hoses, Idle improved dramatically. The other biggest instant improvement I had was the O2 sensor. Replace that as well. You'll have to spend some time tracking the issue and testing things. Good luck!

mak · #3 11-08-2010, 04:46 PM

Among other checks , it may be a leaking Ac pod , rectified the needle will stay pegged to the left side ,engine in neutral or park Do update as you progress .
mak
103

david s poole · #4 11-09-2010, 12:00 PM

basically when you pull the ovp relay you kill the power to the fuel injection computer.the fact that it won't run at this point usually means that you don't have enough fuel dialed in at the adjustment tower.try turning the 3mm allen wrench about a quarter turn clockwise [push down to contact the adjuster]and see if that allows engine to stay running.i suspect that you have vacuum leak which is leaning out the mixture too far at idle and causing the stall.

MBeige · #5 11-09-2010, 12:14 PM

Mark,

When replacing the spark plugs, remember to get the correct non-resistor type. If #2 and #5 cylinders are bad and has fouled plugs I would check those first before tackling a broader problem (OVP) since the OVP controls many aspects of the system.

That could also be caused by multiple problems at once. I remember from our discussion the previous owner drove it as far as he could go but not really maintain it as we would. So many things might have been neglected.

You could break the spark plug wires when yanking them the wrong way. I got a tool with P/N 103 589 00 37 00 to properly remove the plugs from the car and prevent breaking the high tension wires.

Mike Murrell · #6 12-26-2010, 11:50 PM

Quote:

Originally Posted by MBeige

Mark,

When replacing the spark plugs, remember to get the correct non-resistor type.

I read this repeatedly for the 10 years I've been on this forum.....non-resistor plugs only for the M103 motor.

This site now sells Bosch HR9DC - a "resistor" plug. Likely the same elsewhere.

Where does one find the now defunct non-resistor plug - Bosch H9DC/H9DCO or Beru 14K-7DUO.

MBeige · #7 12-27-2010, 01:02 AM

Quote:

Originally Posted by Mike Murrell

I read this repeatedly for the 10 years I've been on this forum.....non-resistor plugs only for the M103 motor.

This site now sells Bosch HR9DC - a "resistor" plug. Likely the same elsewhere.

Where does one find the now defunct non-resistor plug - Bosch H9DC/H9DCO or Beru 14K-7DUO.

My local dealer sold me a set few months back.

lee polowczuk · #8 12-27-2010, 09:06 AM

resistors are ok.... copper core is mandatory