bball1911

My 2002 C240 has roughly 120,000 miles on it.


First I will list the situation followed by my question. Please skip this paragraph if you want to jump to the question. It started going into limp mode randomly and would not go above 30. I would turn off the car and it would drive normally again until the issue would kick in. I was not able to drive over a mile without the car going into limp mode. I was getting error codes P0300, P0304, P0305, & P0306. Due to it being the entire left side of the engine I was able to determine that it was an exhaust issue resulting in a back pressure issue. I have since pulled off the catalytic converters and determined that the driver side is clogged and the passenger side is on its way there.

Since my cats are off of the vehicle I can easily get them swapped for new ones or have a pipe installed to eliminate them. What is the best way to go? As of now the body is in rough shape due to rust on the bottoms of the door so it is not worth putting Mercedes cats on. I do see there are aftermarket versions rated for the car. Am I better off with:

1) Installing new Walker universal cats (or another comparable model, recommendations welcomed)

2) Eliminating the cats (what modification would be needed to fix the O2 sensor readings)

3) A different option I am not thinking of right now.

Any advice would be welcome.

Gramma_Benz

I just replaced my primaries with Walker Cats, but in CA we cannot run without cats. If I could delete them I would.

bball1911

Thanks for the reply. I am in MN and there is currently no testing done here. Do you know if deleting the cats will throw error codes and cause any performance issues?

02C240

The federal Clean Air Act prohibits replacing cats with pipes. Improper removal of a cat could result in fines or imprisonment.

bball1911

I appreciate the reply but I am asking about how the car will react to the other options, not the Clean Air Act and how that would impact me.

Roman Duque

Hello, my name is Roman and i bought a c240 2 years ago with many problems, And i can tell you 1 thing leads to another. The first thing i changed was the PCV valve (left bank Lean), 3 codes went away. Then i changed the EGR valve (right bank rich) - all the codes went away. I then removed the Catalytic Converters because they were roasting my engine (clogged) Plus the trash from the Catalytic was breaking apart and clogging my Muffler!. Power increased and mileage increased. The O2 sensors are 2 upstream (by the motor) and 2 downstream. Do not cut these off, they must read something to Communicate with the ECU. All these problems were from using Crappy gas (all High End cars require Premium Fuel). And not changing the oil on time. I love this car now. The people that sold me the car cannot believe how it runs, and now they have an 800$ payment every month on anew car. The GERMANS think of everything. Alot of people regret "Upgrading" to the Bigger Mercedes. This V6 is Bullet Proof .

Roman Duque

Just dont remove the 02 sensors. And i guarantee your muffler is clogged if your Cats are trashed..

Roman Duque

The o2 sensors are probably toast, my Catalytics were reading 487 degrees on 1 and almosy 600 on the other! nothing survives these temperatures.

silentdub

Those temps are common on most vehicles.

silentdub

Bypassing the cats won't cause any drivability issues at all but your rear O2 will be throwing a P0420/422 and P0430/432 code because it will think the cats are bad. Hence the reason fr needing to replace mine. The code can be tuned out of course but you'll have to send the ECM out for tuning.