Well, this has been a nightmare

But before I go on, thanks to all who have contributed so valuably to this. And now the dirt...

The certified MB repair shop I had previously so counted on has now failed us in a) diagnosis and b) price points. They maintained that the major malfunction here was spark plug / wire - related, which was clearly not the case. Second, they wanted more than $1k for the tune up. Finally, they told us that the cc was not the issue, even when we mentioned it as a possiblity. So we moved it. What made the most sense to me since the inception of this thread has been the cat failure on pass side, which led to the multi-cylinder error codes. Hence we have since had it towed to two other locales nearby (thank you very much, AAA Plus - excellent value). Consensus among other two shops has been cat failure, with the last guy telling me the thing is completely clogged up. I didnt indicate to either place what people were saying on this forum. So much for the certified folks...

Best estimate is $700 - 5 for parts; 2 for labor. I dont think this is unreasonable, necessarily, but compiled with the other $700 we already paid for plugs and wires, things are getting excessive.

Should I have our new 'trusted' guy (a mom&pop shop with a rep for timely and reasonable service) look at the o2 sensor also? I am almost scared to know what the repair bill for that will add up to. Where is it on the 320? Would replacement of the passenger side cat make o2 sensor replacement easy?

Argh. Terrible timing for all of this. Anyone interested in a 99 E320 with 100,087 miles? I know where one is for a bargain

 

Hi,
Any good shop should be able to get to the bottom of this very quickly.

Although I do not favour the catalyst as being the problem (you have reported no rattling noises when cold) it should be a quick and relatively inexpensive job to eliminate the cats from the diagnosis.
You seem to suggest that the cat on the passengers needs replacement....or are you simply suggesting that in IYHO cat failure is the most likely scenario. You say "all clogged up"

For the cat(s) to be the problem it is either a. Ineffective, b. Blocked.

a. O2 sensor levels will confirm whether the problem is an ineffective precat.
The main cat doesn't give feedback to the fueling system so can't be the issue.
if the precat O2 feedback is wrong it may of course be the O2 sensor(s) that is wrong.

b. If blocked this can be determined with a simple airline blow test after dropping the cat part of the system. Not sure if your system is totally separate LH to RH or whether part of the system is shared. If separate is the "steam" coming out of the tailpipe after starting on a cold morning similar on both exhaust pipes? A visual inspection down the manifold connection to the cat is also a good check if the garage has an endoscope or on some models you can actually see the cat brick without special tools.

Precat failure has been a problem on some MB cars and the consequences of this "uncommon" failure CAN BE disastrous since bits of the cat can be ingested by the engine. I do hope that this is NOT the case. The next check will help eliminate this possibility.

When the plugs were changed what colour were they. All the same and looking correct colour or different on some cylinders and black/oily? If so the question must be why? If so what colour are the new plugs after they have now been used for some miles and at the same time what are the cylinder compression pressures. If the compression pressures are OK at least no damage has reulted from ingestion of bits SHOULD this turn out to be a breaking up (not blocked) catalyst.

IF THE CAT IS "ALL BLOCKED UP" THE QUESTION MUST BE WITH WHAT AND THIS MAY INDICATE OTHER PROBLEMS IN THE ENGINE. HAVE YOU ACTUALLY SEEN THE BLOCKED CAT?
In addition the O2 sensor may / or may not be OK. It all depends on whether the stuff that has blocked the cat has also poisoned the sensor. Sensor tip colour and condition are an important guide but the most important thing is the voltage off the sensor.

Unless the above statement is true I would go back to the beginning and redefine exactly what the problem is, what the car type and history is, what has been done and cancel / reconfirm what codes exist and under what conditions they reappear plus if your cars diagnostics support (I'm sure they will) what the conditions were when the CEL illuminates as recorded in the |flash" memory. This may just be a consolidation of info exercise but this will help you when engaging other(s) into the discussion.

I'll then have another go at determining what is most likely wrong.

So just recapping.....

What are the O2 sensor readings? If the garage can't tell you they haven't checked!
Has the injector wiring been checked for insulation damage?
Fuel rail pressure OK? If so, once again what pressure was recorded?
Good fuel? How many miles tank refils since problem started?

Good Luck.

100k miles is no big deal....but history of the vehicle and problem is very important. Don't spend money on expensive replacement parts till you have data to confirm the diagnosis UNLESS you have DEEP pockets AND IF THE CAT IS CLOGGED YOU NEED TO GET TO THE BOTTOM OF WITH WHAT.

Stuart.