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sdawg1177 04-07-2011 10:37 PM

87 300E Rough Idle/Stalling
I have a 87 300E and I have been having some issues. The issue will not always happen. I can always start the car, sometimes I have to push the pedal other times it is just a turn of the key. After I drive the car for 10 min or so my car will start to idle rough (sometimes) when I come to a stop and will not stall till I push the pedal down hard. If I just push the pedal lightly I can continue to drive with a little hesitation and a rough idle. It seems sometimes I can put the car in nutral and rev up and it will idle out fine, then again sometimes the rough idle will continue. When it stalls out it takes 10-20 min of cranking and waiting before it will turn over.It also seems that when I am cranking there is NO fireing going on just turning. When it happens to start everything is normal and problem dose not return for a day or two.

I have replaced plugs,wires,cap,rotor,fuel filter,air filter,oil and oil filter. I would like to get some advice on where I should start next. May be someone has had the same issue. Like I said this problem dose not happen all the time, it's weird. any advice would help.

Thank You.

mak 04-08-2011 12:11 AM

suggestion:with a 103 engine its best to be assured that the OVP and FPR relays are in perfect condition for further diagnosis ,very best is to have new units,same holds good for all the fuses , new brass type.These three ageing components do cause weird symptoms in the CIS -E ,from there on you may check for a leaky injectors including the cold start one and temperature sensor.
Is the fuel accumulator new?

lsmalley 04-08-2011 04:54 AM

make sure you don't have a loose boot that lifts up on the plug on occasion. recheck them and make sure they are all on tight.

Ferdman 04-08-2011 08:19 AM

sdawg1177, when was the oxygen sensor replaced last? A faulty oxygen sensor can cause the hesitation symptoms you describe. As for difficulty starting after the engine has been running I would suspect a faulty crank position sensor that acts up with high engine bay temperature.

sdawg1177 04-08-2011 10:26 PM

I have checked all spak plug boots, they were all good. Also I pulled the OVP fuse and it also was good. I am having trouble finding the EGR valve. I am trying to make sure all vacume lines are in good shape. I drove today with no problems at all. Like I said I am having weird issues.


Jim_P 04-09-2011 11:42 AM

Any smell of fuel? how did the plugs look when you took them out? Thats what my car was doing when the EHA valve went south. Only did it once in a while like the engine was loading up and I was smelling raw fuel when I parked the car. Once I replaced the valve both problems went away.


sdawg1177 04-09-2011 05:51 PM

All six plugs were black. What is the EHA valve and where is it located? I do not smell gas when I park it. After It stalls and I am cranking I do smell gas but no fireing going on. Like I said in my OP it seems that I have to do 10-20 min of cranking before it will fire up.

carat 3.6 amg 04-09-2011 07:27 PM

My 300e had a similar problem a few years ago. It would start and drive for around 15 minutes, then start to hesitate, lose power, and then die.
Turned out to be a faulty ignition coil, when it got hot the windings inside would break down and not produce a proper spark.

abaddsm 04-11-2011 01:14 PM

have you pulled and checked your idle air control valve?

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