C280 Running Rough Need Help With Codes

[Crowe]

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.

[mbdoc]

P1 132 could be causing the P0 30? codes.

Either a vacuum leak, bad fuel press regulator, OR air mass sensor is causing the P1 132.

Most likely the front sensor is reacting to the P1 132 as well.

P0 400 & P1 700 are emission codes & would have effect on the running problem. UNLESS the EGR valve is stuck OPEN.

[Arthur Dalton]

First easy check with those codes would be to remove the front engine cover and look for a broken/cracked white plastic vac line under the cover . This line goes from the intake across the engine to the SOV for the EGR valve....... so, this would bring up the EGR code and the leak would also bring on the others. This hose is a common fault on that engine and should be replaced with a full length rubber one..
As you have plans for a plug change , I would also recommend changing the three plug connectors under each coil..another common fault on that engine..
.......also, use ONLY F8DC4 plugs ...

[Crowe]

Thanks for the prompt replys and suggestions. I cleared the codes which turned off the Check Engine Light. Today I replaced the plugs and the car is now running smooth. It passed the state emissions test with flying colors.