Intermittent rough idle and poor acceleration

[handyjay]

I thought I solved my 92 300E rough idle and poor acceleration problem but it has returned. It is acting the same as last fall when I replaced the O2 sensor and then engine performed great. Now 5 months later same poor idle and performance but it comes and goes. I replaced O2 with Bosch unit. Do these often fail when new? I thought I replaced the OVR last year but after checking records I did not. Could the over voltage protection relay cause intermittent problems? Stumped!!

[Ferdman]

When did you replace the fuel filter last? A partially clogged fuel filter can cause the problems you are experiencing. Recommended fuel filter replacement interval is every 60,000 miles.

[handyjay]

Have not considered the fuel filter. Only have 50,000 miles but it is still 26 years old. The quality of fuel is an issue. I try to avoid ethanol fuels but not always possible. This car has part time usage as it is stored for 3 months at a time between being driven for 3 or 4 months. Purchased 3 years ago with 35,000 miles. I don't think the previous owner had the filter change but I have all the service records and will check it out. Filter is cheap and I will replace just in case.
Thanks for your input. If it solves the problem I will post result.

[lsmalley]

92 300E w/ 50,000 miles?!?! The problem is that that car needs to be broken in