89 300SE Idle problem along with A/C woes

[giewont]

I needed some guidance on where to begin troubleshooting a idle problem my Dad's 1989 300SE W126 has. First off, the car has 47K original miles and I just replaced the cap, rotor, spark plugs, air filter, Oil Filter.

What I am seeing (or feeling) is a slight 50 rpm fluctuation when car is in gear (550- 650rpm). It idles around 800rpm in park. NOt sure if this normal or what. ALso, it sometimes has a slight hestitation when starting from a stop light but then launches rapidly. One thing I was going to replace next was the Fuel filter but not sure after that. From the searches I have done on the forum, some suggest the Fuel Accumilator.

The other problem is the A/C. It was converted to 134 but it is no where near cold enough to defeat the Central TX heat. I have been considering converting it back to R12 and wanted to know the tips, tricks, and warnings the experts have here on the forum. I know the system needs to be flushed and the oil changed back to Ester from the PAG installed for the 134 conversion. Any info would be appreciated.