W210 P170 & P173 Codes. Help!
 

I have an ongoing CEL situation with my 2000 E320. The codes suggest the MAF. I first tried cleaning the existing MAF to no avail and have since replaced the MAF with what appears to be a "good" replacement that I procured from the local pick 'n pull. I cleared the codes and installed the "new" MAF and drove the car for about 50 miles, shut it down for a half hour or so, started back up and no CEL. YES!!! Fixed...oh, but no. The CEL came back on again. I am due for state emissions inspection and this is becoming an exercise in frustration. In searching, some said the cure was in the MAF replacement, some with a gas cap cleaning or a new cap. A friend suggested that it may be a vacuum leak issue. I'm baffled and need to get an inspection. Any suggestions? Thanks in advance...

It is always helpful to post the trouble code meanings. Service manuals have very specific trouble shooting procedures for each code. Also post why you feel the MAF is the problem.

P0170 "fuel trim bank 1", P0173 "fuel trim bank 2". I feel that MAF is the problem because it is a very common problem and many in this forum have had the same codes pointing to the MAF. Hope that helps...

An unmetered air leak could cause the fuel trim to push the system towards rich. Unmetered air is anything past the MAF.

High fuel pressure / liquid fuel leaking from pressure regulator to intake manifold could cause fuel trim to push towards lean.