89 420SEL CEL on and sluggish performance
 

Hey Guys,

Just wanted to pick your brains on this problem. First off the car in questions is a 1989 420SEL (FED CAR) and has about 255k miles on it.

A friend wanted me to look at it and see if I could find out why the CEL light is on and why it was sluggish in performance. I started out by checking the duty cycle and it was 100% or .08V at X11 pin 2-3. Looking over section 07.3 of the MB manual it says to check the O2 sensor. Since the owner couldn't remember when it was replaced, I replaced it with a Bosch replacement. The light is still there, the performance is still somewhat sluggish. I checked the Air flow potentiometer and found no voltage present at pin 1-3 or 2-3. I can unplug the connector at the potentionmeter and the idle does not change at all. Also, there is alot of fuel present in the mixing bowl. It looks like someone has been messing with the idle control screw and the CIS injection looks to be replaced. The OVP was checked as well, no rattle and the fuse is good. I have checked the grounds at W10 and W11 location. It looks like it may be the CIS-E control unit. Does anyone have any other suggestions or a good CIS-E Control unit I can use to test or where to purchase rebuild one cheap?

Thanks.

Hi. Just wondering.... what is a "federal" car? :confused:

non california

Anyone? I am sure someone has seen this before.:confused:

Federal cars turn the CE mil light on ONLY for O2 sensor problems!

What is an CEL light? What does it stand for? I might be helpful if I knew it : ))..

ZCC,

CEL stands for "Check Engine Light".

MB DOC,

It has a new O2 Sensor, I just replaced it yesterday. Why does the X11 Connector only show .08V DC? And why is there not at least 4.5V DC at the Air Flow Position Sensor? I ask this because I went thru some of these tests on my 300SE.

This monrning I had a heck of a time starting it up, it took several minutes of cranking before it finally started and ran but only with the accellerator depressed. It seems like it is running lean but the fuel bowl is wet.

Does anyone else have any other suggestions? They would be much appreciated. :confused:

Strange, all of the S class of the MB from 1986~1991 in Kuwait doesn't have an CEL light. Where is that light located? If possible to post a pic of it. Thank u.

ZCC,

It is the first light on the right-hand side of the instrument cluster (right below the speedometer where all the indication lights are). I can't take any pictures at this time.