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!

Peter, I'll agree that OVP relay could be at fault, and I overlooked that component in my musings.

In my car, it would have to be some kind of an intermittent OVP problem, since the tach always works and the idle is always proper when cold. The tach and idle speed only malfunction when warmed up, but not always. I've had no problems since the weather turned really cold. I'll have to keep digging.

HomrRunPark's OVP fuse may be out, since tach is out all the time.

Checking the OVP relay, and fuse, would be worthwhile, and a relatively cheap fix. Of course, the question would remain as to what caused the OVP relay to trip originally.

Thanks for the additional information.

Best Regards,
Jim

Jim:

The solder in the relay cracks, causing intermittant contact. Usually also causes the relay to get too hot as well, making things worse. May work fine cold, and open up 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!

Peter,

The OVP relay will be on my 'have a look at' list soon.

Best Regards,
Jim

Hi Sam
I have the same problem , after searching found your thread.

can you tell us how you eventually resolved the problem and what parts were to blame.

thanks it would really help me to sort mine out.

Keith

Psfred and JimH,

I have the 87 300D 603 912 engine non turbo 138K Mi and the having the opposite problem very low cold idle speed that is still a little low when warm but runs fine otherwise. Also to note I have no tach on this model..

After doing search on threads it appears I may have electrical vs mechanical issue since several months ago this happened breifly then went away so I don't want to mess with IP settings just yet.

Since that time I replaced injectors, GP's filters ran cleaner through the system and did filters again.

So this AM removed two wire plug at back of IP cleaned the contact (tho not coroded) and reconnected. Started - ran slow - stalled actually restarted and then ran at a slow idle. Removed plug at back of IP - no change in idle speed. Seems to point to idle speed sensor on/near flywheel?

Since this is non turbo I cannot locate any idle speed controller/knob etc anywhere in engine compartment. Also what does OVP stand for and where is this relay located? Below/behind the fuse panel in the engine compartment?

All help and replies appreciated.

Carl

Over Voltage Protection. It should be under the hood, driver side, behind the rubber engine compartment seal. It should have a red top, about 1-inch square.

My speed control is under hood, driver side, rear. There is a round 1-inch knob, with numbers, which is the idle speed control adjustment. However, if there is no change in speed with the two wire plug on or off, I would suspect either the flywheen sensor or the Electronic Diesel System computer.

I don't know enough about non-turbo to be certain, but I would guess that turbo or non-turbo could use the same electronic idle speed control.

Best Regards,
Jim

Thanks for the feedback - I have no red relay on drivers side nor anything with a knob to turn, but on the passenger side behind the firewall cover behind the battery I have the Klima Relay, and two others one large black one that starts with 004 545 and says 6 Zyl Diesel & ELN Control on it in front of the Klima (same size as the Klima) and then a square relay to the side that with a clear cover. All the connections are fine as I removed and replaced the relays.

The other thing on the passenger side behind the kick panel on the floor next to it there is a connector point but no electronic control box so it appears I don't have an EDS module so I either have a basic control system or they hid it somewhere else.

I have the 603-912 engine micro fiche (just need to gain access to the reader) so that is the next step in this adventure.

Thanks for the assist Jim and it is appreciated.

Carl