Convinced problem is plugged cat - PeachParts Mercedes-Benz Forum

bobboyer5 · #1 08-29-2003, 01:59 PM

I've been posting topics recently concerning hesitation on anything but light acceleration. Upon really dedicating time and effort to this over the past 2 days, and carefully assessing symptoms, I've narrowed down the problem to a blockage of some sort in my left cat. My ride is a 77 450 SEL German spec car, 64K miles, well maintained, but when I got it, 11 months ago, I thoguht I had a hole in left cat and went to Midas. They put in a generic new one on that side. I thought I detected a very slight loss of power after it was installed, but dismissed this as imagination.

Well, it's goten worse. And now it makes noise every few minutes. Sometimes contant (like marbles inside), soemtimes not. And the exhaust noise changes with degree of acceleration or throttle on idle. It's definitely from that side.

My fuel/air mix is good; plugs are good; fuel delivery good; vacuum good. The hesitation or rythmic loss of pwoer doesn;t appear always in the first minute or so, but as I drive along, it becomes evident. to the point that I can't accelerate without using an extremely light touch on pedal.

I'm relatiely certain that it's blockage or whatever is creating back pressure which prevents forceful acceleration. I COUL go back to Midas, and argue that it should be replaced under warranty. But is there some kind of 'home remedy' that I can try to reduce the blockage - either internally, or by blunt force from outside. Again, I'm certain that the cat is the source of my problems.

Well??????? Alternatively, might I just remove he 2 cats altogether? Florida no longer has inspections.

psfred · #2 08-29-2003, 04:58 PM

This is the same car with the unconnected O2 sensor?

Replace sensor and verify that is it working properly -- if it is way off, it will cause intermittant lean running (or rich, but that won't cause you any performance loss!).

Cat may be melted if it was running too rich....

Peter