Date registered: Jul 2010
Vehicle: 1995 C220
Location: Missouri, USA
Mentioned: 4 Post(s)
Quoted: 210 Post(s)
On a side note, if it is a vacuum leak that is the problem, that would show up as a lean condition, because the car is trying to suck in unmetered air, so o2 sensors report back a lean condition, causing it to go full rich. If I understand you correct, you are saying it is reporting a rich condition and trying to go full lean.
Also, I wouldnt just go changing all the vacuum lines just because. It will only leave you disappointed when it doesn't fix the problem.
What you could have happening, is some leaking injectors dumping too much fuel, or even an exhaust restriction can cause it to run rich, or a faulty MAF. MAF can be tested easily if you have a scan tool that can spit out how many grams/second it is flowing vs RPM. Basically, your engine is 2.3 liters, therefore at 600 RPM your engine should flow 2.3 grams/second at the MAF. If you idle at say, 750, punch that into the equation (2.3X750)/600 = 2.87 g/s. If you are idling at a different number, substitute 750 with whatever you are idling at. Your MAF should flow within 5 % of this number, so between 2.7 and 2.9 would be considered good. Anything more or less can be the result of a dirty or faulty MAF. Hard part of checking that is finding someone with a scan tool that will show the live data.