Rough idle on start up

I have a 1989 300E with 710,000km on it. The car runs great. When I first start the car up (when it has been sitting over night or for a long period of time) the car runs very rough. The car will shake and sometimes stall. There are times I need to start the car 3 or 4 times before the car will stay on and when it does the rpm's are very low and the car feels like it is going to stall. This happens in warm or cold weather. Sometimes it starts up great when it is cold outside. After a few minutes of warm up I will start driving. After a few minutes of driving the car stops shaking and it runs great. I've had this problem for a few months and cannot figure out the problem.

I have just changed the dist cap and rotor, both fuel pumps and fuel filter.
Spark plugs were changed 8 months ago and the wires were changed.... it has been a while (3 1/2 years ago).

Please help........

[mctwin2kman]

Test the Water Temp Sensor. It is what tells the CIS-E Controller the engine temp to adjust air and fuel for cold starts and also when the engine reaches operating temps and then again when it gets hotter than normal. It lets the CIS-E system enrich mixture and raise idle for cold starting and idle. It also tells the controller when the engine is at temp so it can do its thing with adjusting idle air flow and mixture via the EHA.

Thanks for the info. So where is the water temp sensor located and how can I test it.

Also could the EGR valve have anything to do with it?

Thanks

Fab

[Mike Murrell]

If my math is right, you have about 440,000 miles on the motor.

I'd wonder about the condition of valve guides/seals. When these wear, oil gets thru to the spark plugs. If this is indeed the case, the car can run rough until warm as the oil that's settled on the plugs has to be "burnt" off by the secondary side of the coil.

The 103 motor seems to guise oil consumption fairly well, so taking a plug reading may not tell you as much as you'd think.

If your oil consumption is high, I'd suspect weak valve stem seals or valve guides.

Just another opinion.

[Monomer]

Originally Posted by mctwin2kman

Test the Water Temp Sensor. It is what tells the CIS-E Controller the engine temp to adjust air and fuel for cold starts and also when the engine reaches operating temps and then again when it gets hotter than normal. It lets the CIS-E system enrich mixture and raise idle for cold starting and idle. It also tells the controller when the engine is at temp so it can do its thing with adjusting idle air flow and mixture via the EHA.

How would one test a temp. sensor?

[spriro]

Is the Water Temp Sensor = Coolant Thermostat ??

[A264172]

For an 89' 300E it is this: http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1FX0MB1RS1QN0XMV1M&year=1989&make=MB&model=300-E-002&category=C&part=Water+Temp.+Sensor&appEngines=_any
You can look it up under the "buy parts" tab at the top of the page - under your year and make - under fuel injection.
It tests like this:
Ohm's range from the temp chart in the /Engine Manual-Combustion Manual-07.3 Mechanical/electronic gasoline injection system (KE injection)-121 Testing electrical components of KE injection system. page 60

Temperature °C........Resistance kΩ
-20........................15.7
-10.........................9.2
0............................5.9
10...........................3.7
20...........................2.5
30...........................1.7
40...........................1.18
50...........................0.84
60...........................0.60
70...........................0.435
80...........................0.325
90...........................0.247
Same resistance values apply to KE intake air temp sensor.
I think this chart applies to these 2 sensors for all KE systems but don't know for sure.

[mctwin2kman]

Yep that is the chart and the sensor.

Located on the right hand side of the head in the sensor cluster, while facing the engine. In the front between the front of the timing cover and the air cleaner.