Mercedes Benz 300E Running Rough
Victor520
03-14-2013, 02:44 AM
Q. Vincent, 1987 Mercedes Benz 300E 3.0 liter SOHC with 182,000 miles. Bosch KE3-jetronics fuel injection Continuous Injection System (CIS). All of a sudden, after filling up with gas, it started running rough. Gas mileage dropped significantly, it never was any good. I added two bottles of injector cleaner and the next fill up used Texaco System 3® gas to see if that would help.
I changed the plugs, they were pretty badly fouled but the problem still persists. When I look at the new plugs they are getting fouled with loose carbon building up on the electrodes. Idle speed is about 500 rpm when the accelerator is in the idle position but when it is pushed the idle speed falls and sometime the car stalled. This is a problem at stop lights.
Also, when the accelerator is pushed slightly but before the throttle plate starts to move and the idle switch is releases by the linkage the engine hunts between 400 to about 800 rpm. This continues until the throttle plate starts to move when the accelerator is pushed then the engine speed picks up and off we go. Also there is hesitation when the accelerator is pushed.
Note all this happens when the engine is at temperature. During warm up the idle speed is higher and the problem does not exist.
What have I looked at:
The throttle linkage seems to be tight without any play.
Accelerator cable is loose but nothing binds.
Using high mileage 10W30 oil, maybe the valve seals are going bad, never been replaced or has the engine had a valve job.
Looked for vacuum leaks but probably could look further.
Any ideas or where to look or are the manuals that may help trouble shoot the problem? Does it sound like injectors and is there a way to clean them for a do it yourselfer? Any suggestions or help would be appreciated.
Art
A. I guess the first thing I would suggest is to replace the fuel filter. You may have gotten some dirty fuel and the fuel filter is partially clogged.
http://z.about.com/d/autorepair/1/0/4/D/42003493.gif (http://www.xcardiag.com)
The injectors in a CIS injection system are not electrical, they are mechanical. The injector relies on fuel pressure to open and a fuel distributor supplies fuel to the injector at the proper time. Very much like the distributor in an ignition system.
Inside the injector is a calibrated spring designed to open at a specific pressure. Over time these springs wear out and allow the injector to open too soon. This causes a number of driveability problems, such as you are experiencing.
At best, these injectors are not very good. They are prone to clogging and are not very tolerant of dirty fuels.
They can be tested and cleaned, but not on the engine. There is a special cleaner/tester that cleans and checks the spray patterns and "break" pressure.
http://z.about.com/d/autorepair/1/0/8/9/42003885.gif
The chamber is filled with a cleaning fluid and the injector is attached to the tester. Then the injector is pumped up with pressure and the spray pattern can be seen. The pressure gauge indicates at what pressure the injector opens at.
Brand new injectors should always be tested before installing. At times I have gone through more than 50 new injectors in order to find only six good ones.
Another possibility is the Engine Coolant Temperature (ECT) sensor B11/2. If it is telling the PCM the engine is colder than it actually is, the engine will run rich and cause the type of spark plug fouling you describe.
http://z.about.com/d/autorepair/1/0/5/D/78098720.gif
B11/2 Coolant temperature sensor (EZL/CIS-E/2E-E)
B2 Air flow sensor position indicator
S27/2 Deceleration shut-off microswitch
S29/2 Throttle valve switch, full load/idle
S29/2x1 Connector, throttle valve switch
X11 Diagnostic socket/terminal block (circuit TD)
I changed the plugs, they were pretty badly fouled but the problem still persists. When I look at the new plugs they are getting fouled with loose carbon building up on the electrodes. Idle speed is about 500 rpm when the accelerator is in the idle position but when it is pushed the idle speed falls and sometime the car stalled. This is a problem at stop lights.
Also, when the accelerator is pushed slightly but before the throttle plate starts to move and the idle switch is releases by the linkage the engine hunts between 400 to about 800 rpm. This continues until the throttle plate starts to move when the accelerator is pushed then the engine speed picks up and off we go. Also there is hesitation when the accelerator is pushed.
Note all this happens when the engine is at temperature. During warm up the idle speed is higher and the problem does not exist.
What have I looked at:
The throttle linkage seems to be tight without any play.
Accelerator cable is loose but nothing binds.
Using high mileage 10W30 oil, maybe the valve seals are going bad, never been replaced or has the engine had a valve job.
Looked for vacuum leaks but probably could look further.
Any ideas or where to look or are the manuals that may help trouble shoot the problem? Does it sound like injectors and is there a way to clean them for a do it yourselfer? Any suggestions or help would be appreciated.
Art
A. I guess the first thing I would suggest is to replace the fuel filter. You may have gotten some dirty fuel and the fuel filter is partially clogged.
http://z.about.com/d/autorepair/1/0/4/D/42003493.gif (http://www.xcardiag.com)
The injectors in a CIS injection system are not electrical, they are mechanical. The injector relies on fuel pressure to open and a fuel distributor supplies fuel to the injector at the proper time. Very much like the distributor in an ignition system.
Inside the injector is a calibrated spring designed to open at a specific pressure. Over time these springs wear out and allow the injector to open too soon. This causes a number of driveability problems, such as you are experiencing.
At best, these injectors are not very good. They are prone to clogging and are not very tolerant of dirty fuels.
They can be tested and cleaned, but not on the engine. There is a special cleaner/tester that cleans and checks the spray patterns and "break" pressure.
http://z.about.com/d/autorepair/1/0/8/9/42003885.gif
The chamber is filled with a cleaning fluid and the injector is attached to the tester. Then the injector is pumped up with pressure and the spray pattern can be seen. The pressure gauge indicates at what pressure the injector opens at.
Brand new injectors should always be tested before installing. At times I have gone through more than 50 new injectors in order to find only six good ones.
Another possibility is the Engine Coolant Temperature (ECT) sensor B11/2. If it is telling the PCM the engine is colder than it actually is, the engine will run rich and cause the type of spark plug fouling you describe.
http://z.about.com/d/autorepair/1/0/5/D/78098720.gif
B11/2 Coolant temperature sensor (EZL/CIS-E/2E-E)
B2 Air flow sensor position indicator
S27/2 Deceleration shut-off microswitch
S29/2 Throttle valve switch, full load/idle
S29/2x1 Connector, throttle valve switch
X11 Diagnostic socket/terminal block (circuit TD)
adam4102
03-15-2013, 02:29 AM
hi,
welcome to this forum site. Mercedes Benz 300E is very faster car
purchase this car and drive it .it is very popular car .
-----------
2013 MERCEDES BENZ SL-CLASS (http://www.ezdia.com/EPAD/2013-MERCEDES-BENZ-SL-CLASS-PRICE-REVIEWS/7980/)
welcome to this forum site. Mercedes Benz 300E is very faster car
purchase this car and drive it .it is very popular car .
-----------
2013 MERCEDES BENZ SL-CLASS (http://www.ezdia.com/EPAD/2013-MERCEDES-BENZ-SL-CLASS-PRICE-REVIEWS/7980/)
adam4102
03-15-2013, 02:44 AM
hi friends,
Mecedes Benz 300E
http://cars.tokuhara.net/cars/oldcars/300e/300emoda.jpg (http://www.automotiveforums.com)
Mecedes Benz 300E
http://cars.tokuhara.net/cars/oldcars/300e/300emoda.jpg (http://www.automotiveforums.com)
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