'91 300ce Stalls When Engine Warms Up - PeachParts Mercedes-Benz Forum

Jeff & Jo · #1 01-30-2006, 04:28 PM

HELP!
My wife's 1991 300CE (135K, exc. condition) runs perfect with one exception...when the engine is fully warmed up she stalls (doesn't die, but almost) and runs very rough until about 10-15 mph...then runs fine! I have changed the wires and put in BOSCH Platinum Plus 4 plugs, run Techron cleaner through it, and it was fine for about 2 weeks. Now its the same old story. Runs great until I stop. It idles fine until I press down on gas to go and then it starts to die out, no power, etc. until speed gets up over 15MPH...then fine again. Also, I haven't been able to get HC levels low enough to pass emissions test: Need to register 1.2 and lowest I can get is 1.8. (It had been up to 2.8 before I started working on it) Any suggestions? Many thanks to all!

A264172 · #2 01-30-2006, 04:44 PM

Do you have an m104 engine in that? I dont know too much about that type... but my gut reaction would be a bad 02 sensor or a bat water temp sensor (part of fuel injection system that tells the computer how hot the coolant is) or possibly a fuel distributer problem. Did this happen suddenly? Does exaust smell rich?

dave_rose69 · #3 01-30-2006, 05:29 PM

Jeff: Now that you have installed those snazzy platinum 4 plugs for 26.00+ plus tax, get ready to throw them away, or try to get your money back claiming the parts guy sold you the wrong plug for your car. Ive also heard they break up and fall into the engine. You most probably have a resistor type plug installed now, and thats very very bad. Go see if there is an R in the plug model description, the "R" means resistor. You probably already have resistor caps on your HT wires (metal caps) and now your running two resistors on each plug. Get the correct plug requirement for your engine from your owners manual, gap them at .032 exactly, lightly grease the threads when putting them back and torque them in. I would also order a new Ignition coil from www.*************** (Look at your original coil and Make sure what side bracket you have.) These tiny Bosch coils only last around 10 years at the most. If it has a sheet metal stamped centersection, chuck it....
If your spark color is orangy red, not whitish blue, thats the answer. Good spark is white hot and you can hear it snappin. Dead givaway: Your new plugs helped for a while, but because your spark is weak, they are getting contaminated with unburnt hydrocarbons, Ill guess on closer examination, they will have these little whitish tan spots on them now that looks like sand. So the plug is getting fouled, and because coils die slowly, the last two weeks that have passed by caused the coil to deteriorate even more.
If after the right plugs and coil change doesnt help, write back...
dave.....
If your battery is older than 4 years, chuck that too, and clean up the battery terms bright and shinny before you install the new battery

"93" MB 300TE 4matic 187,000 miles
"85" Volvo 740 Turbo Wagon
"85" Honda Limited Edition GoldWing

suginami · #4 01-30-2006, 08:22 PM

He's right on the money on the plugs.

I don't know if they are specifically the cause of your engine stalling, but you will be completely unable to diagnose the problem until you get the proper Bosch or Beru, non-resistor, copper core plugs.

In addition to doubling the resistance, platinum plugs are specifically not recommended by Mercedes on your engine. They run badly on platinum plugs.

Ferdman · #5 01-31-2006, 07:26 AM

Jeff, the Owner's Manual lists a Bosch F9DC0 spark plug for the 1991 300CE. The local MB dealer advised me to run Bosch F8DC4 spark plugs in our 1991 300CE, and they perform well. Part of the engine hestitation problem could be due to a bad oxygen sensor ... they should be changed every 60,000 miles. A new one eliminated a similar hesitation problem I was having with our 1991 300CE.