M103 Drivability Problems - PeachParts Mercedes-Benz Forum

#1 10-29-2003, 02:15 PM

I've been reading about the various problems with CIS engines. I came across this in the Mercedes-Benz E-Class Owner's Bible and wondered what the experts think about it. If this has already been discussed, I apologize in advance.

'Some M103 engines develop a slight hesitation off the line when the engine is cold. They may also cold start instantly and then die, but restart easily and then continue to run. By adjusting the fuel distributor lower chamber pressure to .45 bar instead of .4 bar, both of these symptoms tend to disappear. The car also seems much livlier off the line.

You are not really richening the mixture when you make this adjustment. Instead the adjustment is compensating for basic wear and tear and any unmeasured air leaks that have developed over the years. You need a CIS fuel pressure gauge to measure and adjust the fuel pressure. If you reset the EHA, the idle mixture should also be checked and adjusted.'

stevebfl · #2 10-29-2003, 04:18 PM

My only problem to changing design parameters is that it is often used to compensate for other poor adjustments. Similar symptoms can occur when the airflow plate base height and concentricity are skewed or the piston depth is improper.

#3 10-29-2003, 05:33 PM

Steve,
I have a '91 300E with 63K miles on it. No adjustments have ever been made to the CIS system or any other system. The car has always been treated with TLC and the only thing that's ever been installed that didn't have an MB part number on it is Mobil 1 in the entire drive train.

This summer I began having problems trying to start the car when the weather was hot. Now it's cooled off and the car starts, dies and easily restarts. Once started, it runs like new.

Perhaps there is some part that is going south but I'm wondering if it isn't just an accumulation of individual things that by themselves wouldn't be a problem but when added up, create driveability problems.

stevebfl · #4 10-30-2003, 08:12 AM

My experience would suggest the former.

Things just don't wear out together and one day cause a problem. Something changes causing that problem. To redesign the system rather than solve the problem will likely eventually lead to special, really hard to solve, problems.

#5 10-30-2003, 08:20 AM

Thanks Steve.