M103 ('89 300CE) difficult starting solved
 

Just want to pass this info onto others who may have the same "trouble".

Several months ago, my 1989 300CE (M103 engine) developed a characteristic where it was extremely difficult to start. It would start up fine, in the normal fashion, but once I let up on the gas pedal, the engine would die. It became progressively worse over time. Same problem, if the engine was cold or warm. I leaned to get really good with the brake/accelerator pedal dance. Once the car was on the road, it ran fine. Then one day, I discovered that when starting, if I "gunned" it up to about 4,000 RPMs, then it would run fine, (usually).

I have my car serviced religiously by Enrique at MB Motors and had him take a look at it. The first two times I took the car to him, he couldn't fix the problem and did not know what caused it. He adjusted this and that, but the problem always returned straight away.

I was this close (holding hand up with thumb and index finger about a half inch apart) to selling the car and purchasing a Toyota Highlander Hybrid. Finally, last Friday on a day off of work, I took it in to Enrique again and told him that it just had to be fixed and it was getting really, really "bad". His little computer showed no faults, so he started looking elsewhere. We took a look at the distributor cap, which was okay...but he didn't like the look of the rotor. It was really "chewed up".

After he replaced the rotor, everything is now fine! Runs like brand new again. Love that guy (Enrique)! I really dread the day he retires and am not looking forward to that day at all. Oh, he also told me that if I do go ahead and get a Highlander Hybrid to replace my truck and 300CE...that I should keep the 300CE anyway. He says it is in really good condition and "will never go out of style". At almost 210,000 miles, he says it is barely broken in. Hard to believe that it only had 75K miles on it when I purchased it from the original owner eight years ago.

Now, if I can only convince him to fix my cruise control.

Ours had the same problem. After replacing:

-temp sensors (both)
-coil
-distributor cap
-rotor
-idle control valve
-adjusting air meter plate (was jamming)
-various rubber tubes
-CPS (Crank Position Sensor)
-OVP relay
-Some fuses

It now runs great!! :D It was having the same startup/idle issue as you had.

My method of parts throwing paid off. ;)

15 out of 20 times the problem is the cruise control amplifier, 3 out of 20 the problem is the actuator, 1 out of 20 is the column switch, and 1 out of 20 is the brake bulbs or its connections.

Good Luck!!

It sort of works...sometimes. I can set it and it will sometimes stay on for a few miles, other times kick off pretty quick. Any idea what to check? Something I can replace myself? Thanks.

It's always best to check the basics first, ignition system for sure. Thanks for the write up.

Well, the easiest and certainly the cheapest are light bulbs. Make sure you're using the correct, European bulbs. Even though a replacement GE or Sylvania bulb may have the indicated cross-reference code number, they draw slightly different amounts of current, and that's enough to affect the very sensitive cruise control in precisely the way that you describe. Intermittently, unpredictably, sometimes immediately, sometimes not for 30 miles. BTDT.

Huh??? You've lost me. Light bulbs affect the cruise control? What bulbs are these that I should check?

Now that I think about it, the only bulbs that have been replaced are brake light bulbs. And, if I remember, (it's been awhile), I did replace one of them with an auto store purchased bulb.

ONLY the BRAKE bulbs place a role in the cruise control circuitry. The ones in the tail lights. That's it.

Keep in mind, it is highly unlikely they are the ones causing your problem, since your cruise control works some times. 15 out of 20 times the problem is the cruise control amplifier.

Do a search, you will find everything you need.

This is a very old topic and there are many discussions in the forum.

Good Luck!!

cc
 

three soultions to look into
rear brake bulbs
All fresh fuses
cruise control amp solder connections resoldered.