My wife's 1994 C280 is running rough and I am trying to determine how best to fix the problem. The car has just over 190,000 miles on the clock. I ran the OBDII codes on the car and can report the following:

• P0134 O2 Sensor CKT No Activity Bank 1, Sensor 1
• P0400 EGR Flow Malfunction
• P1132 Manufacturer Control Fuel Air Metering
• P0133 O2 Sensor CKT Slow Response Bank 1, Sensor 1
• P0300 Random/Multiple Cylinder Misfire Detected
• P0306 Cylinder 6 Misfire Detected
• P0302 Cylinder 2 Misfire Detected
• P0304 Cylinder 4 Misfire Detected
• P1700 Manufacturer Control Transmission

I am planning on replacing the plugs this weekend. Any ideas of other issues to address based on the codes above. Let me also point out that we purchased the car used. A few times the car would start to run rough when you hit the brakes hard and then immediately accelerated. On those occasions if you pulled over and shut the engine off and then recranked it the engine would run smooth again. Now the engine is running rough all the time. We have been running the middle grade of gas and once we added the premium grade to the tank it is running a little better but not as it should. I need to fix the problem soon since it is emissions testing time for the tag renewal. Any thoughts or suggestions are welcome.

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• 2001 E320