wow thats some good stuff ill make sure to try all of them out thanks alot man..... one more thing i asked the mb dealer and they told me the year model that my benz is that they dont have an idle air control valve...... if theyre wrong could you possibly send a picture of what it looks like and where its located?
it starts without having to press the gas but then i rev it up a little and when i let it go it drops down to a grand and then stalls after. it doesnt stall right away it feels like its trying to keep working but gives out.
Yes, it is possible that your car does not have an idle control valve, mine is 87 260E. I saw the video, this behavior is similar to what I had with my 260E with the exception that mine would turn on and idle and when I tried to rev, it would not go beyond 2000 and would hesitate like yours.
Did you observer the air sensor plate when you are doing this ? Is that plate hesitating too and making that motorcycle type noise ? Check vaccum as soon as you can, it should be between 16 and 22 inch Hg right after it starts and for whatever time you can keep it at idle. Could be very much related to vaccum, in your car the idle mechanism may be vaccum dependant.
Did you check the resistance on pin 1 and 2 of the air sensor potentiometer when you gently press it when the car is off ? That should tell you if this is a problem with the sensor.
sorry but whats a potentionmeter? is it the 4 studs? coming from the mass airflow sensor? is that what their called potentionmeter? and what do i check it with just a regular voltage meter or what.... sorry im not really familiar with all this.
I was checking the manuals and found out that it is possible that you dont have the same fuel injection system as the mechanical system I have as well as cars upto 92, yours is a 93. Does it have a LH fuel injection system ? This is very different from what I have. In your car the air flow sensor is electronic and does not have the potentiometer I was talking about. I believe there are some articles here that mention how to test a LH air sensor, I could not find it in the manual, because it is the currents that change as opposed to resistance. And I saw that the LH system's air sensor has 4 pins perhaps rather than 3 as far as I can remember on mine, this is what triggered me to look. Send me an email at saumil@swbell.net and I can send you some of the manual pages that may be helpful, will help locate the components and also provide explanation of how various components interact and make the engine run.
In these systems, you almost have to change the entire air flow sensor, you can clean it somtimes but it does not last. This sensor and its circuitry will affect idling, so if there is one thing you want to change blindly, this would be the one.
Based on the description of your car in the manual, it looks like the coolant temperature sensor could still be a potential problem, and this you can still check the same way, it is a device which will reduce resistance as the engine warms up.
The signals from the airflow sensor and the temperature sensor go to a LH control unit, which if has a problem could also cause the engine to stop.
Check vaccum also to rule out catalytic converter.
Also this car has a temperature sensor in the CAT converter that would turn on an indicator if the CAT is overheated, which is what I would assume would occur if it was clogged. So if you did not see the light, specially when it was warm, then it is less likely to be the CAT. The assumption here is that the LH control unit is functioning normally and can interpret the KAT's temperature sensor and activate the light correctly.
There is also an air intake temperature sensor, and this should work similarly as the coolant temperature sensor. This should be on some hose that goes to the air filter box. This sensor should also reduce its resistance as the air temperature increases, you can test this with a hair dryer. This signal also goes to the LH control unit. The air/fuel ratio is determined by this unit, so assuming the air flow is detected correctly, the other thing which can cause a wrong ratio is the temperature reading, both the air intake and the engine temp.
Upon reading more on LH system, it looks like the car may go into a limp mode if the MAF sensor is disconnected. Does the engine run better with the air sensor cable disconnected ? If it does, then just change the air sensor.
Also it seems like you can do some basic voltage measurements on the connector of the sensor. Unfortunately, I could not find the exact pin assignments in the manual for your car (104 engine). I could only find it for 119 engine and that showed a 5 pin connector rather than 4 that you mentioned. But one of the pins would be ground and one would be 12V. For ground, keeping the car off, you can do a resistance check with any other ground point. A zero resistance would indicate the ground pin. For 12V, you can turn on the ignition switch without turning on the car and check for 12V using the voltage setting on the multimeter. Positive terminal of the meter is on the connector and the negative can be connected to any ground point in the car. One of the pins should have 5V and this too can be checked as the 12V test. The fourth pin carries the signal from the sensor to the computer (the other 3 brings voltages from the computer to the sensor). In order to test this pin, you will some how have to insert a wire along with the connector and put it back on the sensor, i.e. T off this connection. When you turn on ignition without turning the car on, you should get about 1V on this pin with respect to any ground point in the car. Upon turning the car on, this voltage may go to about 1.5V and then as you gradually rev up, the voltage should smoothly increase, the max you would get to is about 4.5V on full throttle.
Linear Mode
