PeachParts Mercedes-Benz Forum - View Single Post - 97 E420 feels strangled over 4500 rpm

rjk · #8 05-30-2011, 04:13 PM

First CAT.
No code for me.

I'm not saying definitively that it is your CAT, just something to check based on the similarity of a problem I had last year.
My car bogged down on the highway at speed.
Then it got to the point (over a few days) where it would not run at speed.
After a short layover of about an hour, it restarted & ran fine for about a week.
Then it coughed & died & would not run over 20 mph.
I initially assumed ignition since there was oil present on most of the coils & it was due for a tune-up which I performed (removed & cleaned coils, R&R plugs, etc). No joy.
This forum pointed me to the CAT stating classic symptoms, they were right.
Knocked on CAT, it rattled, removed it & the car was back to normal.

Your bog at speed is the only similarity so far but is worth knocking on the CATs to see if either one rattles. They are not cheap and there are two (rt & lft). It is the forward CATs that seem to fail & block things up. The dealership will probably recommend replacing both. That can run north of $2k so you don't want to go and purchase something without confirmation (rattle).
I found some Bosals for about $600 on the web, it isn't a hard R&R. I did it on my back in the driveway w/the car up on jackstands. I did not replace both but am expecting the other to fail. At least this time I will know the preliminary symptoms & can catch it early (I hope).