Check engine light 93 300E2.8

The check engine light came on today. Seems to drive OK except maybe a little increased idle speed at times. Temperature and oil pressure are normal. When I pushed the code reading button under the hood, the LED flashed ten times. Does anyone know what this means? What should I check?

Have not received any replies but I thought I would update my problems in a little more detail. Except at idle, the car performs great. Gas mileage seems to be the same as always. The car has 65,000 miles, had the car since new. The idle problem is intermittent. At times, no problems, at other times, surging to 1000 rpm and then back to 500 rpm within a few seconds and repeating. It seems that having even a small load (such as having the transmission in "D") takes away most if not all of the idle problems.

There also seems to be a new symptom--sometimes, but not often, when trying to start the engine, you can grind on the starter for seconds with nothing firing at all. Even though the car is turning over, even the tach does not register any rpms. Ten seconds later, it starts immediately.

I would appreciate any help or tips. I plan to take the car to a pro next week but just wanted to understand what my problems and/or options might be.

[Aaron]

Funny, but my 300E 2.8 doesn't have a check engine light, and I don't recall seeing one on any one I've worked on. BUT..As far as your idling problem, I would first check the overvoltage protection relay which is behind the battery with a red cap on it. There's a fuse in there which can blow, leading to problems like you describe. OR...Situation #2, (not pretty) is the wiring harness. I just replaced my harness in my 2.8 a couple weeks ago. I had been having trouble with it idling rough, not wanting to start, and misfiring under acceleration. Couldn't pull any codes, so the wiring harness was the obvious culprit. Also renewed all three coils while I was in there. Runs like a champ now! The harness is about $600, and labor times may vary, depending on diagnostic time. Since I did mine myself, I got out the "good" way!

[mbdoc]

Code 10 means the computer thinks that the AIR MASS meter isn't sending correct info. This can also affect the idle.
The part # is 000-094-05-48 list $= $355. Installed many of these for this problem!

Thanks for the info. I will probably put an overvoltage relay on tomorrow. Since I have been told that I should probably carry a spare anyway, it seems almost like a free one before taking the car to the local gurus. But I doubt that it will help. I think there is a rule that nothing cheap ever helps.

As far as the air mass meter, I did not think it had that much to do with idle (but you are the experts and that is why I asked you). The car runs great at any time except at idle in P or N. It has normal power and response. I just filled it and the mpg was within one mpg of the average over 65,000. It seems like a simple job to install. Does it take some adjustment after installation or is it a do-it-yourself job?

I have looked at the wiring because I have heard of the problems. It looks like new with no cracking or flaking of the insulation. Also, I do not get misfiring or rough idle, just a surging when in P or N. But I will certainly look at it if need be.

The check engine light is the far right one in the row of lights at the bottom of the instrument cluster. I never knew it was there it until it turned on but after looking, it does come on when the key is first turned and all the lights are checked.

[Arthur Dalton]

The CD wiring diag. show both check eng. lamp [A1-e26]
and push button diagnostic plug with led for code reading
on Cal. 124.028 [93-300E, 2.8]
Don't have the code #'s, but someone else may.

This will probably be too long but just want everyone to have the information. Seems like I have fixed my problem. I replaced the air flow sensor (from Fast Lane) and it now seems almost back to where it was. I say almost because it seems like in the "limp mode" it had a little more acceleration off the line but that might be my imagination. Maybe an extra rich mixture and not meeting emissions in this mode? There also seems to be slight differences in the driving of the car. I cannot quite explain them but evidently the sensor has not been quite right for some time. Anyway, no more check engine light, no more fault codes.

Regressing a bit, after my last post, for some reason I cannot explain, I tried starting the car with the air flow sensor disconnected. The car ran exactly the same as with it connected. At that time, I decided it must be bad. I could not believe how well the car performed (except at idle as I have described before). Started properly, drove nicely, no loss of power. Just would not idle properly. If this is a "limp mode", I hope to have this type when I get to be 90 years old!

Before doing the air flow meter, I did put in an over voltage protection relay and it was exactly as I expected–no change at all. But now I have a spare for what I understand is a troublesome item.

As far as I can see, the insulation on my wiring is good. I can find no indication of any flaking or cracking of my wires. However, the plastic locking mechanisms on some of the smaller connectors seem to crack and fall off when I try to take a connector off around the engine.

As far as the fault codes for pre-OBDII Mercedes, I found a site that seems to give most of them. The years for the different models seems a little mixed up but you can figure it out by looking at the engine size. The site is:

http://www.batauto.com/MB.html

It also has codes for a lot of other cars as well. Go to:

http://www.batauto.com/technical.html

Thanks for everyone's help. I think this information exchange is terrific. And thanks to Fast Lane for very reasonable prices. I also got a new headlight at a price I thought was unbelievably low. (Just the old original equipment–hardly ever drive the car outside the city limits or at night.)