i am new to the whole car repair thing and am trying to learn it, and i have a couple of questions about my temp sensor( 190E 1992/2.6). i think i need a new one, but perhaps someone could confirm that for me. also i am confused about the color of the sensor. everything i have seen on this site or others says that that car should either have a green sensor at the back of the head drivers side( thats where mine is) w/ 2 plugs for the harness to plug into, or a black one w/ 4 prongs on the intake manifold( i think). mine is on the head and is blue!! what gives. definatly blue not faded green ect... the reasons why i think i need a new sensor: the car has gotten incresingly hard to start, sometimes i need to step on the gas and crank at the same time, when it turns over the rps are way high 1500 +/- 200. they come down when it warms up. i have had a rapid drop in gas milage from aprox 18 mpg to 11 mpg. the o2 sensor was replaced as well as the plugs. the car is not getting up to temp at all, not just because its cold out either(20 degF at night). the temp gague needle has not hit 80degC in at least a week. thats where it is usually in winter time, and it takes at least 15 min of idle time to get off of 40 degC. the other thing that i noticed is that the speedodometer needle has started to jump arround. when its cold its the worst and when it warms up its almost unnoticable. i know its a 50 $ part, and my car drives like ****. any help is welcomed. i want my BENZ back.

By your description, I would start with a new thermostat.
I believe yours is sticking open.
That's why it takes so long for the engine to come up to temperature.
Install a new one ( may want to flush the cooling system while you're at it ) and see what happens.

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2007 C 230 Sport.

As Manny said, the problem is more likely to be a stuck closed or very lazy thermostat. Find someone with an IR gun and shoot the water outlet after driving long enough to normally warm up the engine. If the IR gun is about the same as the temp gage, and both are well below 80C, it's the thermostat. If the IR gun shows normal temp, 80C, but the gage reads low, the problem is the temp gage sensor, not the CIS-E/EZL temp sensor.

I am interested in the configuration of your CIS-E/EZL temperature sensor, but it's not clear from your description what you have. It is the most rearward sensor along "sensor row" between the cam cover and inlet manifold. Does it have a four-pole barrel connector? If not, can you provide a description of the connector or connectors, including number of poles.

The second from the rear sensor has a single pole connector, and it feeds the temp gage. If you remove the connector with the engine hot, the temp gage should react.

The third sensor from the rear is the cold start valve temp sensor. On early cars it actuates the cold start valve at 15C or below. Mine is blue. Later cars have a 60C or below cold start valve temp sensor, and that I believe it's a different color. What color is yours?

Pull each connector off and check the pins/receptables for damage or corrosion.

I've had an intermittent problem with speedometer needle wiggle in the 75-80 MPH range, which causes the cruise control to surge. It doesn't happen up to about 70. The speedometer cable on 190s is essentially sealed and cannot be lubricated, so the only option appears to be replacement. Mine was replaced on warranty, so it's fairly old, but doesn't have that many miles.

Last year I removed it from the transmission to check cable operation, and it spun smoothly with little friction.

Age and low temperatures can take a toll. When the weather gets warmer you speedometer wiggle situation may improve.

Thank you for the advice. However, before i could preform any of the tests that Duke 2.6 and Manny recomended my wife got into an accident. It doesn't look major at this point. I should have it back on the road soon. It wasn't her fault. I have spent most of my day dealing with the associated problems. I will try what was recomended and post another reply when i have some information to report back.