That code indictaes a fuel trim problem. The adaptaion values will show how the system is compensating, rich or lean. If they are pegged at the 1.32 compensation value, then it's likely that the Air Mass Meter is faulty. If they are pegged low at .67, then it's likely that the fuel pressure regulator is on it's way out.

You need SDS to read the values.

Suppose the fuel trim adaptation value is 1.32 or over 1.10. Then connect a "known good" Air Mass Meter and drive the car, reread the values. If that corrects it, install a new AMM. This is what a good mechanic would do. If the problem is NOT solved by the AMM, then reinstall the unit. By paying for a solid diagnosis, you'll save a ton on replacing good parts. It sounds like you'll eventually replace both O2 sensors and a bunch of other stuff before you get the problem solved.

Why did you replace the EGR? The code P0170 is fuel trim and the devices that commonly fail that regulate the fuel trim do not include the EGR.

Also, the O2 sensors have their own series of codes, the P013X codes. If you're not seeing those codes, why are you starting your diagnosis with replacing O2 sensors?

I know that a vacuum leak can pop up a P0170, but on that car, it's the AMM or pressure regulator about 90+% of the time.

c230 p0170
 

My first codes about a year ago where for connection on the secondary o2 then fuel trim and primary o2, yesterday the car add no code, the fuel filter was over due by 40.000 miles. I couldn't feel any bad idle so I didn't think of any vacum leaks,the fuel trim and o2 codes did give me the impresion that of a low fuel to air ratio and the Egr valve came to mind since the code came on only after some fair amount of driving and the codes is a Emmission one, the valve wasn't replaced. I'll resend the secondary o2 that I ordered and I am all the wiser for now. the car been this young now I figure the o2 must be due for renewal for the fuel injection to work correctly, my privious car, 84 Audi 5000 285,000 miles had the o2 light come on every 40,000 miles or so and just add to reset the switch behind the dash, changed it only once, I'd figure it be simular. I am going to need SDS to read the values next time If I sense it really needs it, so far everything on this board has help to narrow it down without extensive equipements and thanks again.

I'm having difficulty with reading your post, so I'll wing it...

The O2 sensors are not a "periodic" replacement item as it might have been on your old Audi. My own 1998 C230 has never had an O2 sensor replacement, and will not until they are required. The emission and FI systems in your 1984 Audi and your Mercedes have little in common as far as diagnostics are concerned.

As to idle quality, a failing Air Mass Meter often gives no idle quality problems and when it's really on it's way out will usually give a hesitation above 4500rpm or so.

It sounds like you prefer to keep throwing parts at it until the codes are cleared. Good luck.

97 C230 code P0170 in 01 & 02
 

Thank for the hint on what to look for when the air mass sensor goes. The only small hesitation that I can detect is about when the car just warm up at idle if that indicative of anythings!

p1070
 

I'm back to let everyone know that my proplem with the engine check light seem to be resolved . :dj:

So, are you going to tell us the cure, or is it a deep, dark secret? ;)

p0170
 

Its not a secret low fuel was due to FUEL FILTER!!!!!!:dj: :dj:

:) To up date you on my Benz , I did purchase a air mass insert for $99 and run the car in second and third gear to reach 4500 rpm and voila! The car works like a charm, now the proplem i get is the second 02 sencor give me when it get wet a fault code, I tryed to replace it but could not budge it. my question is there a special wrench to get a good grip on it?
by the way thank you all for your informative insights.