On my 1993 300D 2.5 turbo, USUALLY when i start it in the morning after a cold New England winter night the car will start without hesitation, the tach will work perfectly, and the engine will run strong and smooth with perfect accelleration.

After the car is driven for a while, and the engine is at normal operatiing temperature, when i turn off the engine to go into a store and come out 10-15 minutes later the engine will take an extra second-second and a half to start, the tach will rest at zero, the engine will idle a little rougher and the car is extremely sluggish, it feels as though some of the cylinders or the turbo is simply not working, as the car severely struggles to get up to speed and often barely makes it up hills.

Any ideas guys? I'm lost here and want this problem fixed. Thanks for all your help!!

__________________
-Sam
93 300D
210k - Sold, but not forgotten.

BUMP

No One has any ideas?

__________________
-Sam
93 300D
210k - Sold, but not forgotten.

While I have an idea what's wrong, I don't know what it is specifically.

My SDL has an intermittent idle problem. Sometimes, ususally when hot, it will begin to idle erratically. The the idle will not be steady and the tachometer will jump around, so it's not just the gauge. Then, the tachometer will drop to zero and the idle will drop also.

Taking off usually brings the tachometer back to life, and the jumpy idle may, or may not return. It works OK from a cold start, though.

It's an intermittent fault somewhere in the electronic idle control. I haven't found yet if it's the sensor, the controller or the idle speed actuator.

That all said, I beleive that your idle speed is also controlled electronically. The zero tachometer would lead me to believe that your idle speed has dropped to its mechanical low limit, usually 500-600 rpm, which is quite low. At that speed, it may well vibrate more than ususal. It might also be a bit slower to start, as the fuel rack is not calling for as much fuel. Sluggish could simply be the extra time to pick up from a 500 rpm idle.

Check, or have a technician check, the electronic diesel control system that controls the idle.

Best Regards,
Jim

Thank you, any idea on $$$, Parts & Labor?

__________________
-Sam
93 300D
210k - Sold, but not forgotten.

Sorry, I have no idea about $$.

Mine is intermittent, so it's about impossible to troubleshoot until its next episode. It usually malfunctions while I'm on the road, and behaves when I get back. :p

I generally suspect wiring connectors first, as they can corrode and lead to problems, and it's usually easy to unplug, look for corrosion, spray some contact cleaner and reconnect the plug. Sometimes just the act of unplugging and reconnecting 'wipes' corrosion off the pins and everything clears up, like magic, so it's my starting point.

Going by memory now, and I have a W126 body, your W124 may differ...

An rpm sensor is mounted on the bell housing, below the oil filter, driver-side, and senses flywheel teeth passing under it. If I remember, it is low voltage (2-3 volts) and a variable frequency corresponding with the rpm. A simple voltmeter test of the sensor confirms the sensor as GOOD/BAD.

The idle control actuator on the IP is also low voltage, 2-5 volts, depending on output from the Electronic Diesel System control module. Again, a voltmeter test. I think this test confirms EDS module output.

The EDS module sits behind the front passenger kick panel, right side, below the glove box.

I have not leanred exactly how and where the tachometer obtains its signal. The wiring diagrams show a connection with the EDS. Perhaps a voltmeter test could confirm voltage or lack of voltage to the tach.

There is a 'trim' resistor under the hood, behind the master cylinder, that is set to one of several positions to adjust the controled idle rpm. Uncontrolled, or mechanical low limit, is 500 rpm or so, controlled is 625-725 rpm or so.

There is a plug with two wires at the rear of the IP. Unplugging removes the EDS signal to the idle speed actuator, leaving the uncontrolled mechanical low idle.

As I understand, you can drive the car forever without the tach, and it will idle, although slower, without the EDS functioning.

Good luck
Jim

OVP relay, the idle speed control system isn't working hot.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!