Engine Promlem '94 S320

[akaras]

I wonder if anyone experienced anything like this. I had this car for more than a year.It has 66,500 miles on it. In the last few months I have encountered this problem. While driving at relatively low speed, usually coasting at approximately 20-40 MPH with light pressure on accelerator, the engine sort of shudders and starts to run rough like on 4 or 5 cylinders. It continues to run rough like that indefinitely, I've run 20 or 30 miles like that. When the ignition is shut off and engine is restarted everything returns to normal and the engine runs fine for days or weeks. So far it happened four times. I don't know if the check engine light comes on, who ever owned the car before took the bulb out. I've been to an authorized dealer twice. First time they ran diagnostic check and replaced the front oxygen sensor and a cracked boot on # 2 spark plug. The next day it happened again and I drove it, while it was running rough, to the dealership and showed the condition to the technician. He put the test equipment on and restarted the engine and it was fine. There were no fault codes, nothing in memory, he wanted to do couple more hours for checking and component changing and estimated the bill would run $2500. I decided to hold off on that and consult with somebody.
Does any one know what might be going on. My wife is afraid to drive the car for fear it will die and not restart at all. After four times I'm a little more comfortable but still concerned. I would like to zero in on the problem or I'll have to trade the car.Please help.
Arvin Karas.

Hi Arvin!

What a coincidence! I just experience the same jerky feeling from a running engine but only for a minute and everything back to normal just the otherday. Don't know why but still driving! Mine is a 92'300SEL.Can BenMec help to enlighten both of us? Thanks.

[David C Klasse]

My car did that one time. It was about 6 months ago. I was at a mall, started it and the whole car shuddered the whole drive home. Was not as bad on the freeway. Once I stopped the engine and re-started it again, the problem has never recurred. The idle seemed fine too.
I thought it was the motor mount, but it never happened again! Maybe it's something with the M104 engine?!

[engatwork]

The first thing I would check would be the charging system. On my E320 when the alternator was on its way out I was in stop and go traffic and it started doing something that may be similar to the experience you are having. I will say though that the first sign something was wrong is that the radio would shut off and the power antenna would lower then the car started driving real strange. This may be what is called the "limp home" mode. I don't know. The other problem, especially on the W124, is the wiring harness. Give it time and see what one of the techs say.
Jim
'85 300D
'95 E320
'97 CRV

[Ed Richardson]

If the engine wiring harness is original, that might be the problem. They either have failed and been replaced, or will fail. Check the search function for previous discussions. MB will replace these if approached in a kindly fashion. Ed

[ejsharp]

Arvin... we have an expression here in the States... "That mechanic saw you comming!"

The car must be diagnosed by a reputable mechanic. The problem you describe could be caused by a number of things... for example your air flow meter could be sticking.

I would wait for Benzmac or one of the other techs to offer their opinion.

Smiles.

[JimF]

Arvin,

Same thing happened to my '94 S500. It started to run very rough and the engine 'shook'. I raced the engine and continued to drive. After a few minutes, it slowly went away. I did not shut the engine off.

It 'felt' like it was a plugged injector because it slowly got better after a few minutes. It started immediately, with no warning. It was so rough that you had to keep the accelerator depressed to keep the engine speed up.

Mostly likely, it must have been a bit of 'crud' that partially plugged one of the injectors. It certainly was fuel related.

The only thing that I did that day, was to dismantle the vacuum lines, changeover switches to the AIR and EGR valves. That may have had something to do with it. Maybe dislodged some gunk?

It's only happened once. Very difficult to fix this tpye of problem. Good luck

Arvin,

I just traded an Infiniti that did the same thing. After replacing O2 sensors and running up a huge bill searching for the culprit, they finally found small pin-holes in the EGR tubes. The heat and corrosion from the exhaust gas was the cause. I had previously had the EGR valve replaced for the same symptoms. Good luck!