I read this in an older post. I'm still looking for an explanation as to what the heck is wrong with my car (I'm so mad at it right now). Read the quote below and tell me if that's correct because if it is correct then I'm not going to mess with the fuel mixture. Thanks.

** It would be really great if I could get one piece of knowledge across about mixture adjustments. That one thing is this: any car that has an oxygen sensor (1980 and above) AND is functioning properly can not be made to run better or worse by adjustments.

IF YOU ARE adjusting a car (in this catagory) and are changing the way it runs then the car is BROKE! **

To some extent that is correct, but it depends on which fuel injection system the car has. If your car has the Standard K-Jetronic Fuel Injection System, then any adjustment you make for the fuel mixture, it will change accordingly. If the car has the K-Jetronic E, which is the electronic version of K-Jet, you can still make adjustments, but there are other sensors which will try to keep it in a specific area. You can still make minor changes in the fuel mixture.

Which year and model Mercedes do you have?

I have an '84 190E. How can I find out what kind of injector system I have?

An 84 190E would have the Standard Version of the K-Jetronic Fuel Injection System. You can make all the adjustments you want on this.
There is a Tower which takes a 3mm Allen Key inside the air filter housing, this is where you adjust the fuel mixture.
While you're adjusting that, you may also want to check the Ignition Timing.
The best way to make the fuel mixture adjustment is by using an analog meter, and hook it up between pin 3 and 6, that way you can watch the ossilations of the 02 sensor and make the adjustments accordingly

On any car that has adjustment for fuel, the mixture can be adjusted TOO much(rich OR lean)! Then the computer imput from the O2 sensor won't allow any fuel mixture changes!!
AT this point the car could run better but most likely worse!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Sometimes your ears just burn.

The point to the above statement is that the mixture on all US MBs since 1980 is controlled by the engine management system. If you make adjustments that are felt then the system is broken or overwhelmed. Early cars such as yours had to have a base point set (adjusted) so that the cars controller has equal ability to correct both rich and lean. This is an adjustment but it only can be measured as the cars mixture stays the same and it runs the same. If the mixture changes as it is adjusted then the electronic control system is out of range.

Later cars even set their base adaptation themselves.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

We had a fuel injection problem and the tech replaced the O2 sensor and that was the cure. It had become fouled after the temp sensor for the fuel injection broke.

__________________
David
'00 Mazda MPV Family's car
'83 300D 235,000
'84 109E 175,000
'74 280C 125,000 in garage; needs rehab or sell for parts???