Right on!

Looking at the first post, this mechanic says a rattling under the car could either be the cat or the fuel pump. Seems to me that a good mechanic should be able to differentiate those two -- via fuel pressure test, maybe?

One thing I've learned, from this and other lists as well as my own personal experience, is that different mechanics have different aptitudes and interests. A mantra we hear on this site, from Gilly and other pros, is that proper diagnosis preceeds parts replacement. Some mechanics are just plain better than others at thinking through the logic of tracking down a problem, esp. if it involves control circuits, is intermittant, causes malfunction indicator lights, etc.

Find another mechanic. Folks on this site can help with that. If not, contact a local MBCA officer and ask him/her who local club members take THEIR cars to! I can just about guarantee they'll know who's good.

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Steve
'93 400E

Hi, my turn:
Let's see if I have this right: Truck ran fine, but check engine light was on (I am assuming it was running OK), OK, tech sez misfire codes, lets replace plugs and air filter (good maintenance, I like that, worries me a little (just a little) when maintenance is recommended to repair the vehicle tho. OK, so plugs and airfilter are replaced, THEN the truck runs badly? And check engine light is still on. AND now it rattled underneath, too. Yeah, great. WHAT do I tell you.
Not sure, this is I think referred to as "FUBAR". My thought would be a botched spark plug install somehow, but how? Broke off a sparkplug and he's hiding something? Wrong wire on a couple plugs? Ruined a plug wire? I dunno. Should run better not worse, and now it rattles underneath. Maybe due to a dead misfire?
At this point you may want to consult a different MB mechanic, dealer or a good indy. I guess my first step, well, if it's really just #6 misfire, start there, check connections are correct, plugs are tight, maybe inspect the plugs, who knows what happened. I'd discount the rattling as a "cause" of the problem, maybe an effect not a cause.
The fuel pump I've never heard of one that "rattles", plus it's mounted in the tank.
Gilly

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I took the car into the dealer , they said both catalytic converters need to be replaced and they recommended all 4 oxygen sensors be replaced at the same time.
All of it adds up to some serious $$$$. I am considering ordering parts over the internet but have never done so before. There is such a big difference in price, does anyone know if these parts/places are reliable. Any suggestions?

Silent Mode,

She's a NEW MEMBER, let ask her questions. She came to this forum expecting to be HELPED along with some courtesy from ALL members.

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TOOFAST45

'93 300E 2.8 - 138K miles

I just bought one made by DEC. I have not put it in yet (just got it Monday) but I have looked it over. The dimensions are very similar. The "output" flange is mis-aligned about 1 degree which I hope I can deal with. Probably, but it would be nicer if it was straight. The quality of construction is not as good as Mercedes but it was 1/4th the price, literally. I am curious also what people have to say about the different brands. I never heard of catalytic converters "rattling apart" inside until I got this Mercedes and started using this site. My original Toyata Supra cat is still going strong.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

It's not an uncommon problem. Certainly not limited to Mercedes.
I would not replace both converters if only one was rattling. As far as ordering parts online, you can certainly save money. Just be sure you are ordering the correct parts. Returns are sometimes problematic. Many of the online vendors don't actually handle the parts, they just forward orders to distributors. So they like to charge restocking fees on returns. Also, if you are not going to install the parts yourself, make sure that you have a mechanic that will install owner-supplied parts. Many will not.

Thank-you!

While only the driver's side converter was rattling, the technician told me that both converters were bad..the driver's side was in worse shape!!
What's confusing is that if both were in such bad shape, why didn't my check engine light come on sooner? Why didn't the oxygen sensors detect any problems?
I was also told that while they are pretty sure this is what is causing the problems with the car, it is not a guarantee. So after I change the catalytic converters and the oxygen sensors, they might still find additional problems!!

In my case my cats still work perfectly well, they just rattle under any load. And I also have just one side (I think) making the noise, but mine is all one welded assembly so I have no choice. I think you have multiple unrelated problems. A good diagnostician can sort through all of this. Did the dealer claim that the cats are responsible for all of the symptoms?

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

God, I hope not!!!

[/QUOTE]A good diagnostician can sort through all of this. Did the dealer claim that the cats are responsible for all of the symptoms?[/QUOTE]

He suspects that is the case, but will not offer a guarantee.

Well, I suppose if it is clogged up. I would think there is a way to test this (other then installa new cat). On the other hand, if the cat is bad then it needs to be replaced in any case. Hope they are correct!

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I'm just really skeptical of the diagnosis, doesn't seem right to me, especially given that first the problem (I assume) was the check engine light, THEN after the plugs, etc were replaced, it ran badly. Shouldn't run worse after maintenance was done. Or was it running poorly before the work was done?

Gilly

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Click here to see the items I have up for auction at EBay

Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)

Before laying big bucks for catalytic converters, have the exhaust back-pressure checked! VERY simple operation for any MUFFLER shop & OR repair shop that does emissions repairs. IF the back-pressure is high then have THAT catalyst replaced. WHY replace parts that TESY good?

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

If you're anywhere near NE Indiana I know of a place that installs owner's parts dirt cheap. They run their business out of a little old gas station, but they get the job done. They're good with exhaust stuff. They'll weld pipe, etc. to save from buying a whole new exhaust or even a muffler assembly.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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When I took the car in for the CEL, I told them that there was also a rattling noise coming from under the car. So they did the back-pressure test and that's how they decided that both cats needed to be replaced. I guess what worries me is that no one knows for sure what made them go bad. They keep telling me that the engine misfires would have caused it...but what caused the engine to misfire?? Their answer to that is that if the cats are bad it will cause the engine to misfire!!!
What came first the chicken or the egg??????