Mechanics

WHAT IS REASON FOR FUEL SYS 2 =OL-DRIVE ( OPEN LOOP ) NOT GOING TO CL-CLOSED LOOP WHEN VIEWING LIVE DAT ON DIAGNOSTIC MACHINE ?

2005 Mercedes Benz E350 • 100,000 miles

The vehicles MIL-malfunction indication /engine light blinks at startup and then stays on. The only fault in the ecu is P0300 -RANDOM MISFIRE and P0304-cyl 4 misfire and P0355-Ignition coil e/primary/secondary cct malfunction.
The ignition coil of cyl 4 was swopped with cyl 6, ignition coil is ok as cyl 6 does not misfire.
When spark plug is connected to ignition coil cyl 4 and held against earth point of engine cyl 4 still does not fire.
New spark plugs have been fitted, bosch platinum plugs.
The fire/trigger wire from Bosch ECU is good 1 ohm resistance and the other 3 wires also good.
I replaced upstream lambda oxygen sensors bank 1+2 but not downstream sensors. Pressure in both cats seem to be the same.
The camshaft positioning sensors and magnets have all been changed.
The injector has not been checked for firing and or resistance.
The crankshaft positioning sensor has not been changed.
Compression test has been performed and ok by maritime motors.
The fuel pressure has been checked by maritime motors/agents.
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Regfridey
August 20, 2012.



With P0300 you cannot say cylinder 6 is not misfiring. Random misfire can be any cylinder misfiring and it is possible cylinder # 4 is more prominent and picked up by the ECU.

Trouble codes indicates ignition coil problem, what have you done to test/check them apart from swapping? In this case I don't think swapping would give you the correct diagnosis.

KHLow2008
Aug 20, 2012.
Ignition coil 4 was removed, a plug fitted to the end of the ignition coil and then the engine was cranked to confirm spark on ignition coil 4. The sparkplug does not fire. The same process was done on another cylinder and here the sparkplug fires.
OBD11 is very strict regarding emissions, and my opinion is that the ECU is causing this misfire on cyl 4 as that is the other error code being displayed p0304(cyl 4 ).
I am also of the opinion that the injector may be at fault but here I would need to lift the injector rail and swop it with another injector say bank 1 and then see which trouble code is being displayed.

Tiny
Regfridey
Aug 22, 2012.
4x Magnetic sensors and 1 x camshaft positioning sensor was replaced. Upstream O2 sensors and 6 x new bosch platinum spark plugs have been replaced. Wiring for cyl 4 injector and ignition coil 4 has been confirmed between connectors and Bosch Engine control unit. Fuel pressure has been checked by agents. Come the weekend I will lift the fuel rail to remove and inspect the injectors for cyl 4.

Tiny
Regfridey
Aug 22, 2012.