om602 idle too low
 

Hi all,

seeking your thoughts on my latest issue.
1992 300D 2.5 turbo om602 361,xxx miles. egr delete and pressure wastegate.

headed home from work the other day everything is fine. Rolling on the highway 85mph, AC Blasting. Chillin'

pull off the exit to go up the hill to my house and there's a problem.
sitting in traffic waiting to get through a light and engine RPM are down at idle.
right about 450rpms.

I was immediately concerned so i pulled over real quick and just did a quick visual check under the hood. nothing obviously amiss. no smoke, fumes, leaks, sounds, smells out of the ordinary.

continued on to the house and shut down. Came out later and checked some more. oil looks fine, coolant looks fine, fuel looks fine. fuel and air filters are recently changed.

Apparently nothing wrong mechanically. I've looks all over the linkages and everywhere under the hood and have not found anything the looks out of the ordinary. just the low idle. each time i've started since then same thing with the low idle. Drove to work this morning no problems at all out on the road as long as i just kept my foot on the pedal to keep the idle up a little bit when i was stopped.

any ideas?

My understanding is that the idle on your car is controlled by the computer (in fact, that's all it does now that you've done the wastegate conversion). So that would be a possibility.

Here is the procedure for testing the computer (the EDS):

http://www.w124performance.com/service/w124CD1/Program/Engine/602_603/07.1-1120.pdf

That is my understanding as well. I don’t know much about it. I’ve read a few threads on idle problems. “Hunting” idle seems to be a common failure mode

Just edited my post to include link to test procedure.

Actually here's link to test idle speed in particular:

http://www.w124performance.com/service/w124CD1/Program/Engine/602_603/07.1-2006.pdf

As mentioned above, idle speed is controlled by the EDS computer. Do you have other symptoms of problems, such as an ABS light or intermittent tach? If so, you probably have a bad or failing OVP relay.

no other symptoms that i have noticed. No lights on the dash. tachometer solid steady.

battery voltage good. charging 13.5ish volts at around 1200 rpms

Im with Dieseal300 OVP

Im with Dieseal300 OVP

Check that the connector is firmly plugged into the ELR actuator, the round thing at the back end of the IP.

Sixto
98 E320s sedan and wagon
02 C320 wagon

I have unplugged and plugged the wiring for the actuator a couple times. no change

can someone tell me where the resistance timing plug is located?

i will be working through the test procedure to see if i can isolate the problem.

This may help:


https://www.yumpu.com/en/document/view/36522505/0520-adapting-ignition-timing-point-with-resistance-trimming-plug-to-

Where is the EDS located on our cars? How would one access it?

Should be in the cubby behind the battery. I don’t think the 2.5 turbo has idle speed adjustment. The ‘87 300D/TD has a trim knob by the brake booster, IIRC.

Sixto
98 E320s sedan and wagon
02 C320 wagon

If it doesn't have the round trim resistor, it will have a single rectangular trim resistor. You can change idle speed by changing the resistor.