Hopefully some one can help me narrow my problem down.
I have an 2000 SLK230 with 57000 miles. While I was driving, my "Engine Check Light" came on and my engine power decreased.
I live about 100 miles away from an authorized dealer, so just taking it to the dealer is kinda hard.
I am thinking that maybe it's the O2 sensor (because of the mileage). But, I not sure. Can anyone shed some light.

Thanks Carl
carllittlejohn@cox.net

I had the same experience with one of the 3.2L engines in our ML. Problem was a failed ignition coil module and spark plug wire. One took out the other, but it was indeed an instant fail situation. One second, we had power, the next.....Pinto power.

do a search under AMM or MAF sensor for C230 sedans, if you want to play with it yourself.

also read in those threads about having codes read, maybe at an AUTOZONE for free it one is near you.

warning: there are a few cases where the codes for a AMM - fuel trim malfunction - is not fixed by a new AMM sensor.

Fist let me thank you for your ideas. I'll check with the parts and repair places in my town about scanning.
I just came in from my garage and noticed some things that might help.
1) When my car is at idle, it run as if nothing is wrong. But, if I increase the rpm to about 3,000 rpm, the motor shakes. Like a rocking motion.
2) I checked my spark plugs, all of them are firing. If I remove a plug wire the idle gets real rough. When I put it back on it idles normal.
3) Took off my air cleaner box (with the butterfly valve assembly). No change. The same indication as I mentioned before.
Again, thanks.

You can monkey around with this and waste a ton of money and time on parts before finding the problem. Here's what you need to do:

1. Have the OBD-II codes read. This will steer you toward the right bunch of parts.

2. Once you determine the codes, read the adaptation values to further narrow the diagnosis.

Example:

Code P0170 is a fuel trim problem. Something is failing and causing the fuel system to run rich or lean. By reading fuel trim adaptation values, you can see if it's rich or lean. If the adaptation is maxing out (1.32) then you are reasonably certain that the AMM (Air Mass Meter) is faulty. Replace the AMM and see if the problem is solved. If they are low (.67) then you probably have a fuel regulator problem.

Don't assume a CEL is an O2 sensor. Those are the old days before OBD-II. OBD-II CEL codes number in the hundreds. All kinds of things can account for poor running from misfires to fuel trim problems.

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

Carl.

did you have your SLK fixed? What was the repair if you know?

Ethan, I thought that my car was fixed, but I was wrong. I took it to the nearest MB dealer to get it repaired. They ran a diagnostic test, spend 7 hrs troubleshooting, another 6 in performing the repairs, and it was o.k. for about a month.
MB Troubleshot or replaced the following:
1). Supercharger, Re-shimed the compressor clutch gap.
2). Air Injection Valve (at compressor), Replaced.
3). Fuel Filter, Replaced.
4). Air Mass Sensor, they said it was o.k.
5). Camshaft Position sensor, they said it was o.k.
6). Throttle Position sensor, they said it was o.k.
So, after $773 of labor charges & $412 worth of parts. It's still the same.
I give up. Carl

Why not contact mercedes / regional rep and tell them how much you paid and the problem is back. Even if they make a statement that the present problem could be different from what the car was taken in for, don't let them off the hook.

remember AUTOZONE pulls codes for free and check out www.club202.com
lots of people there modify these cars.


also if you could be more descriptive on exactly how the car feels compared to when normal would help.
Are there speeds or times when the car feels normal, does the tach ever stumble?

I was all set to say that this sounds very much like a secondary ignition miss, (fine at idle, misses under load) but surely a dealer tech would have found this. I'll be very interested in finding out what the final solution is.

__________________
1989 300 SEL that mostly works, but needs TLC

My problem started 5 months ago when I stepped on the gas and my power suddenly decreased. Then my "Engine Check Light" came on. Every time I stepped on the gas, it seemed like the Kompressor was not engaging (decreased power). I took the advise from "Ethan" and John S and purchased a hand held scanner. I hooked up the hand scanner and got the following codes:
P1420 - Air Pump Switchover Valve
P1235 - Camshaft Positioning Sensor
P1525 - Adjustable Camshaft Timing Solenoid

My MB dealer replaced my "Air Injection Valve" at the Kompressor. This took care of the problem for about 5 months and then the same thing happened. I decided not to pay MB $1200 again (only to have the problem reappear), so I went to the “AllData” (http://www.alldata.com/products/diy/) web site and subscribed for one year ($14.95). The web site provided me with the proper Diagnostic Trouble Codes, Specifications, Diagrams, Troubleshooting charts, etc. Everything pointed to the Air Pump Switchover Valve. So, I replaced the "Air Pump Switchover Valve", because that was the first code that came up. Well, I ran the scan again and received the same codes. I shouldn't have gotten the same code for the "Air Pump Switchover Valve" because I just changed it. So, I looked at a MB trouble shooting chart and it said to test the K40 relay. I don't have the special 128-pin test box, so I took the cover off the diagnostic box (upper left hand corner, if you're standing in front of car) and took out the "Relay Module" box. Mostly all of the relays are contained in this box and soldered to a circuit board. Then I had to open it up and find were the K40 Relay was on the circuit board. Wasn't hard to find because there were two BAD solder joints for the K40. I re-soldered the connections and I haven't had a problem since.
Maybe this might help anyone that is having the same problems that I had.
Carl