yet another developing problem 89 300e - PeachParts Mercedes-Benz Forum

lorainfurniture · #1 07-31-2009, 02:19 PM

I recently replaced my fan pulley/housing on my 300e (now to be known as "the wedding car") 2 days later, I started to get some erratic idling, now it randomly stalls out. When I decelerate, the idle just goes lower, lower, then stalls. At stop light, stalls. Starts back up immediately.

I always had a problem with a slightly high idle, about 900-1000 in park.

Now, when it does idle, it idles perfect. (600 rpm)

Just a thought: I forgot to re- install my fresh air tube. the plastic pipe that goes from the air filter housing to the grill. Would that make the difference?

Any ideas on where to start?

tinypanzer · #2 07-31-2009, 08:56 PM

First thing is to make sure your throttle linkage is set correctly, and that the microswitch that engages the idle circuit is indeed being actuated when the accelerator is let up.

If that is working properly, I would start checking for vacuum leaks. There are several places for those on an M103.

pawoSD · #3 08-01-2009, 01:54 AM

When you removed the fan assembly I assume you were bumping/working around the distributor cap/wires....make sure none were disturbed or loosened in the process. Also verify all sensor connectors on the engine....

lorainfurniture · #4 08-01-2009, 03:07 PM

Hi, thanks for the pointers. I was digging a little further in the threads, and I think I am having an ovp relay issue. I gave it a good whack, and the idle jumped for a second before stalling again.

Am I diagnosing correctly? Is there a more scientific way to test ovp?

The micro switch is just an on/off switch, correct? I would just check continuity?

I will re- check vacuum and report, but I think everything is in order.

Arthur Dalton · #5 08-01-2009, 04:38 PM

If the OVP is suspect and condition is intermittant :

Pull the OVP and wrap a wire around the base of pin 30 and another wire around 87e...
Use about 12" of insulated wire for each and strip the other ends.
Install the relay
Start car.

When the problem presents itself, touch the two stripped ends of those 2 wires together and see if that solves the condition or condition changes ....if yes , replace the OVP.

This is a sure test b/c you are in-situ by-passing the relay while the car is running and condition is prsent, so if the problem is intermittant, this will eliminate/confirm OVP -Yes/No.

lorainfurniture · #6 08-01-2009, 06:14 PM

I will test and report. Thanks in advance

lorainfurniture · #7 08-04-2009, 10:33 AM

update:

So I inspected my idle switch. The wheel was half broke and not catching. I gave the wheel a half turn, now the car is idling MUCH better.

I still have this nagging random stalling. I did wrap the wires around pin 30 and 87e. then I noticed I had 2 87e pins, Does it matter?

The problem im having is that the car stalls randomly, so even if I stand next to the car with wires in hand, it stalls before I can put them together. I restart just fine.

It seems to spike a little in idle before it stalls, this morning it did it, with my foot on the brake, the idle spiked to about 1200 or so, then puttered out.

One thing to mention, when the car starts acting funny, I just keep my foot on the gas to keep idle up, (slightly)

Arthur Dalton · #8 08-04-2009, 10:45 AM

Both 87e are the same..just for different feeds.

If you can put a push sw on the wire ends so you just have to press it before the stall is complete.
Intermiitant faults are very difficult to find.

You can also wire the OVP contact pin of 87e with a 12 lamp and ground..if the lamp goes out when it stalls, you know it is OVP feed glitch that has dropped power to 87e ............if it stalls while you still have a good test lamp, you know it is not OVP feed.

lorainfurniture · #9 08-04-2009, 12:02 PM

I think the 12v light might be my best bet. Just to be clear, a wire from 30 and 87e and install a test lamp to those leads?

Arthur Dalton · #10 08-04-2009, 12:28 PM

Quote:

Originally Posted by lorainfurniture

I think the 12v light might be my best bet. Just to be clear, a wire from 30 and 87e and install a test lamp to those leads?

NO...............

Re-read the test.

You have 12v INPUT at pin 30 on the OVP..what you want to know is if the OVP is putting OUT 12V at 87e terminals when the car is running or if it has an intermittant glitch.. [ which is suspect by your conditions]
So, you put the test lamp between 87e and ground...then when the key is ON , the lamp lights and that is output to the systems...if it stalls and at the same time that test lamp goes OUT, you know the OVP has failed at that time and is then suspect..if it stalls and that lamp does not go out or flicker , than the OVP is OK as far as output goes.
Just use that 87e wire I had you install and put the test lamp there and ground the other test lamp lead to a good ground...simple

lorainfurniture · #11 08-04-2009, 12:40 PM

understood, I will test this evening and post results.

Thanks again Dalton, I hope I can return the favor to you sometime if one of your major appliances fail

Arthur Dalton · #12 08-04-2009, 12:44 PM

Or if one of yours fails... and you are having a problem, I can walk you thru it.............

Thanks for the offer, though...............

lorainfurniture · #13 08-04-2009, 01:16 PM

Right, I forgot....
We discussed this on a previous thread..

well, ill get you any part you need at cost..
Or if im ever in florida, ill cut your grass or something..

Arthur Dalton · #14 08-04-2009, 01:32 PM

Yeah,,,cutting the grass is not my favorite , so that's cool..

Do you do Windows ??????...

lorainfurniture · #15 08-04-2009, 02:06 PM

never much of a window cleaner.....

I have installed a replacement window before