engine rock/misfire

[monza3000]

I am new to this so I hope I use the correct format?

My wife’s car is a 1998 E320 W210 Auto, a few weeks ago I had to replace both Cats & the rest of the Exh. system.

Since then I have had an engine rocking from mild to heavy & had a Merc Diagnostic which indicated a problem with Cyl.6 & Cyl.3, a 'friend who is a 'Merc Tech' said it was the MAF, which I changed, this did not work, next suggestion was both leads for 6 & 3, nothing!

I then replaced the remaining leads on my own & still no luck, by the way all plugs have also been replaced, trying to understand why I was having this problem, I then pulled off each coil pack connector while engine running (apart from No.3 as I could not access) & when I got to No.6 there was no change in the engine note.

Thinking this indicated this coil pack; I replaced it only to find I still had the same problem? During the course of all this I noticed that the engine, when revved, spluttered which I had not noticed driving!

I am now down to thinking that if, as I had been told, there is a limp mode, then maybe it is No.3 coil pack that is the problem & this shuts down No.6?

Also, as this all happened following the Exhaust/Cat replacement, is it related? I am positive it is not engine mounts as stated on many American Sites.

So far this has cost me over £1500 & I need some help & advice on this as I am limited as to what I am able to physically do, and if I do need to go to a main dealer, I am probably going to end up paying out another Grand or so!

 

[jaymanek]

not sure but when they replaced that cat did the O2 sensors get changed? These can cause misfres..

 

[grober]

One thing that may have been disturbed /damaged during the exhaust replacement might be the Lambda sensor/s. They control the fuel mixture so this may be causing a misfire?
Jay beat me to it. New problems that occur after any repair/replacement -- the first place to look is where components have been changed.

 

[BlackC55]

Whay did you replace the cats?

 

[monza3000]

Thanks for your quick response, jaymanek, grober, & BlackC55

Regarding sensors stated, the check data only indicated prob in No.3 & No.6 and my Merc Mech started me on the road described! This has 12 plugs & leads & 6 coil packs, I have not seen this before?

I might have slightly given a wrong indication ref. mis-fire as it was a left to right rocking of the engine whilst standing in or out of gear which varied in intensity & was also intermittent, it has now got to the point where it is rocking quite a bit & when I revved it quite high on my drive, it then spluttered at about 3000 revs No starting problems & it drives ok.

I replaced the complete Exh. system, as it was the original at 127000 mls, after a Cat broke up & felt it was necessary to do.

If it went into 4 cyl. mode due to a failure of a coil pack on a cyl, would the power to the opposite cyl then not shut down?

Thanks again you three,
Peter

 

[monza3000]

1998 W210 E320 Weird Engine Problem

When stationary car rocks, pull away & hestation for a couple of seconds then ok, car starts ok, no other faults logged, just had Bosch MAF fitted plus all 12 leads & plugs, coil packs ok. (also new fuel pump)

Told that MB issued instruction/rework saying that some MAF's had to be set up with Engine Management System via computer, anyone heard this?

This all followed a complete exhaust/cat replacement though do not think related.

I am on the point of driving off Beachy Head, please give me a possible starting point!

 

[Dieselman]

Sounds like an HT misfire to me or possible EGR valve sticking open.