engine miss? 1995 e320 104 engine
 

Three days after changing my spark plugs, my engine started running a bit rough....more like a miss when you accelerate.

pulled the codes, got one for a bad 02 sensor..... but no CEL

I have a spare o2 sensor which i should change.... first i will take a look at the plug connections to see if any loosened.

Car ran great with old plugs...and ran great with the new ones until this problem.

any other ideas?

A couple of thoughts.

Did you read the Pin 8 and Pin 14 codes? This may help pinpoint the problem. I too have gotten a code for the O2 sensor, changed the sensor, and had no improvement.

It could be that you put in resistor plugs instead of the specified non-resistor plugs. This puts a strain on the ignition system (in ways I don't completely understand).

The ignition wires could be bad. The three connectors under the coil can experience heat and corrosion, and may need to be replaced.

Maybe the AMM (air mass meter) needs cleaning, or changing.

What about the wiring harness? Has it been updated to the newer one?

newer wiring harness.

i will change the o2 sensor and report back... second option will be changing the connectors....

plugs are identical to the ones that were in there before.....
should have left well enough alone.

other pins showed no codes.

i always bet on the airflow sensor in these cases. (and yes, it was the last of many things I changed in my own troubleshooting mystery). 140 k miles is a great life for them.

changed out the 02 sensor..

engine is the ....still getting the #2 fault on pin 6--- heated oxygen sensor faulty.

will move on the other things..

back to normal for now
 

I disconnected the mass air flow sensor....engine ran the same.

"re-seated" the coil connectors... engine back to normal

I will change out those three connectors... i didn't realize that this should have been done along with the plug change.

******EDIT**** this may have been the culprit or a contributing factor----- one of the plug wires was arching due to an insulation breach..it may have happened when i was tightening the cover.... put electrical tape around it for the time being.

I did notice... that I have one "light blue" coil pack....and two black ones.... maybe i will order that part as well.

thanks all for suggestions and advice...both publicly and privately.

oh..... by the way, the fuel pump relay started acting up on my wife's 300ce yesterday... her car died right in traffic.. i feel bad that it happened..... she was able to start it back up and got home.... i had a spare relay in the trunk....but that didn't do her any good when she lost all systems on a fairly busy road.