1997 E420 Multiple Missfires

mmcfearin · 04-26-2012, 01:37 PM

Mt 1997 E420 is running poorly, rough and loss of power, also poor fuel millage and the smell of raw fuel in the exhaust. I started having these problems at 154K so I had the 150K work done at an indy. Plugs, boots, and all 4 O2 sensors replaced.

I am at 168K now and all problems have returned. Codes show cylinder 2,3, and 8 missfire, multiple missfires, and rear back O2 sensor failure.

I I found all this returning odd but I did use an indy I had never used before, generally I do all my own work after warrenty but got lazzy. So I pulled and replaced all plugs (copper ones spaced correctly now) the indy had installed platnum plugs in an amazing aray of poor gap settings. I also replaced the 3 boots. The O2 sensor erros I figured was just do to raw fual because of the missfires so I have not replaced it yet.

Unfortunatly this didn't correct anything so I went ahead and replaced all 3 ignition coils. This also has not solved anything. I can't see an O2 sensor causing all this and while I didn't get a code for it this seams to me the next thing to replace is the MAF. Ideas?

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Plutoe · 04-26-2012, 05:40 PM

How old are you wires?? Do you have live data capability on your scanner??

MASTERBENZ · 04-27-2012, 05:49 AM

Check fuel pressure...sound like a fuel problem to me!

mmcfearin · 04-27-2012, 08:12 AM

Unfortunatly I don't have live capabilities on my scanner, I am looking at finding a new scanner preferable one that links to a laptop.

I have not thought of fuel presure issues, is there a test I can do for that?

The wires to the coils are original.

Thanks for your time guys.

Plutoe · 04-27-2012, 12:44 PM

Although thoughtful, fuel pressure testing is not easy without the actual values and tools for the locations to be tested.

I would at least start to test the condition of the wires. However I do not have the values. Get a new one and check it's value. Rail and injector fuel pressure issues will normally produce faults. I would also check my coolant sensor----use your AC value test to check that! Just don't get suckered in to a new MAF!!

erashid · 05-06-2012, 11:41 AM

I had the same issue spent over $800 trying to fix at indy's with no luck to finally be the wires.try taking one of the wires on a cylinder that is not complaining with one that does; and see if the issue follows.

04-27-2012, 05:49 AM	#3
MASTERBENZ Junior Member Garage is empty, add now Join Date: Mar 2008 Location: Alexandria, VA Posts: 42 Drives: Mercedes-Benzes: 2005 ML500, 2002 E320 4-Matic, 1993 300E, 1994 E320, AND 1999 C230 KOMPRESSOR	Check fuel pressure...sound like a fuel problem to me! __________________ I'M A FACTORY-TRAINED MERCEDES-BENZ MASTER SYSTEMS TECHNICIAN, ASE (AUTOMOTIVE SERVICE OF EXCELLENCE) MASTER AUTOMOBILE TECHNICIAN, BOSCH MASTER TECHNICIAN, MECP (MOBILE ELECTRONICS CERTIFIED PROFESSIONALS) MASTER TECHNICIAN, AND A L1 ASE & BOSCH ADVANCED ENGINE PERFORMANCE SPECIALIST WITH A MASTER'S IN BUSINESS ADMINISTRATION.

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04-26-2012, 05:40 PM	#2
Plutoe MBWorld Fanatic! Garage is empty, add now Join Date: Feb 2011 Posts: 1,143 Drives: 1999 E300TD	How old are you wires?? Do you have live data capability on your scanner??

04-27-2012, 08:12 AM	#4
mmcfearin Newbie Garage is empty, add now Join Date: Jul 2010 Location: Virginia Posts: 3 Drives: 1997 E420 and 1990 560 SEL	Unfortunatly I don't have live capabilities on my scanner, I am looking at finding a new scanner preferable one that links to a laptop. I have not thought of fuel presure issues, is there a test I can do for that? The wires to the coils are original. Thanks for your time guys.

04-27-2012, 12:44 PM	#5
Plutoe MBWorld Fanatic! Garage is empty, add now Join Date: Feb 2011 Posts: 1,143 Drives: 1999 E300TD	Although thoughtful, fuel pressure testing is not easy without the actual values and tools for the locations to be tested. I would at least start to test the condition of the wires. However I do not have the values. Get a new one and check it's value. Rail and injector fuel pressure issues will normally produce faults. I would also check my coolant sensor----use your AC value test to check that! Just don't get suckered in to a new MAF!!

05-06-2012, 11:41 AM	#6
erashid Newbie Garage is empty, add now Join Date: Aug 2010 Posts: 2 Drives: e320	I had the same issue spent over $800 trying to fix at indy's with no luck to finally be the wires.try taking one of the wires on a cylinder that is not complaining with one that does; and see if the issue follows.

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