Hi there,
I started having problems with my 1991 300 ce as it would run rough and stall. I would wait for about 15 minutes and it would run fine for about a few miles and would start running rough and stall again. I used the obd next to the battery. I got two problem messages which was 27 that was blank and had no info on the diagnostic fault code reading and the second was 34 stating "communication and navigation system". I replaced the ignition module, crankshaft sensor and ignition coil. I went back to the obd to check if the the problem would still show and number 34 was cleared but #27 still kept on showing and cleared it. I then started the car and rpm used to go up to 9 and after all the replacement of parts it went up to 10 on the RPM. Engine sounded great.Then the engine check appeared after running the engine for a few seconds. I then started running the car with the check engine light on and after a few miles it started running rough again like before. Checked OBD and #27 appeared again. At this point I gave up and decided to go to the forum for help. If anyone had this problem before, can you tell me what to do to get it fixed. I got attached to this car, had for 12 years now and the body and interior are in perfect condition. Please help me. Thanks