New quick w124 Catalytic Converter help pls!! - PeachParts Mercedes-Benz Forum

Bigpete123 · #1 07-17-2008, 05:06 PM

Hi All,

Sorry, the title should say "Need quick help".

The car is a 1990 300ce with about 200k miles on the clock. It's on its original catalytic converter.

I suspected that my cat was bad after I failed emissions, developed a rough idle and hesitation.

I suspected the cat because I previously have had to have my fuel distributor replaced, had fouled plugs and bad injectors, leak down, etc. Basically mechanics were scratching their heads trying to diagnose the rough idle after having tons of work done on it- they have either replaced or checked everything under the hood that they can think of. The list is seriously too long to list.

The last time I had it in, the mechanic suspected the cat, but he was very slow so I had to take my car back from him before he could test it.

I just took the car into midas this morning and they are saying it's bad. They tested it by doing a "heat test". They said a typical cat gets hot in the rear when its running. But they are saying mine is "ice cold" near the back indicating that it's not burning up the fumes like it should. I actually could have it backwards (could be cold in the front, hot in the back, not sure).

Not to be an a-hole, but I don't completely trust their diagnosis simply because they are midas. So here are my questions:

1) Is this a valid way of testing the cat? I know people typically do a vacuum test of some kind to determine if it's partially or completely clogged. I have also heard of mechanics simply disconnecting it and running the car to see if the symptoms go away. They didn't do anything like this.

2) They are saying that I can only get a "direct replacement" type of cat... meaning either OEM (no way I'm paying that kind of money) or another after market bolt-on version. They said they cannot use an generic one and weld it in. I have heard of others on the forums using universal ones though... The only concern I have with that method of replacement is that you have to put a lot more trust in the craftsman doing the welding and bending.

I ask #2 because they are saying it will cost $1,000 parts and labor for an aftermarket direct-fit unit. They said it's 2.2 hours of labor.

I asked them if they'd be willing to install one if I found a deal online and brought it in and they said yes. I'd rather not have to pay $1k. Their shop rate can't be more than $75/hr, so 2.2 hours should only cost around $170.

I found this cat that should fit my car. If I bought this one, the total with labor and shipping would only be roughly $450-$500. Any thoughts on this unit, or any other recommendations?

http://www.***************/carparts/mercedesbenz300ce19881989catcocat97171930.html

Not to rush- but I need to give them an answer in the next few hours.

Thanks!!

Peter

mpolli · #2 07-17-2008, 06:06 PM

I bought a Catco and I will not buy another. It was "Direct Doesn't Fit" and looked like it was welded by Grandma Moses after her sight completely failed. There are other aftermarket brands available.

Bigpete123 · #3 07-17-2008, 07:39 PM

great... I already bought it :-(

mpolli · #4 07-17-2008, 09:42 PM

Well let us know how it works out. Maybe she got her sight back.

G-Benz · #5 07-18-2008, 12:08 AM

You never posted the emissions test results...

...you may not have needed a new cat after all...a clogged EGR tube will also cause a failed emissions test...my culprit last year.

mpolli · #6 07-18-2008, 02:02 AM

Here in Seattle they don't test for NOx so it probably isn't the EGR. When my Toyota failed it was the O2 sensor. He had it diagnosed as the CAT so hopefully they were correct! But there are lots of things that can cause trouble. The numbers would help of course but it looks like the money has been spent. Will be disappointing if it doesn't work.

Bigpete123 · #7 07-18-2008, 01:21 PM

indeed it will.

The fact pattern is such that this isn't a wild guess though...

1) Had leakdown/burning oil/bad head gasket

2) Timing was off, injectors, plugs, wires, cap/rotor, fuel distributor, 02 sensor, EHA valve all needed replacement at some point in the past

4) Last mechanic to look at the car suspected the Cat after ruling out vacuum leaks and basically everything else he could possibly think of (diagnostics are $$$). He was slow so I needed the car back before he had time to test it.

5) My symptoms match typical indications of partially clogged cat

6) After doing some research online, the "heat test" that midas did was a valid way of testing the Cat. So assuming they aren't lying, the Cat could at least be to blame for the bad emissions of not my poor running conditions.

So I thought to myself, the fact pattern is there. It's not 100% proven, but it's probable. I'd rather just pay $500 parts and labor having it installed than $250 on an indy shop's diagnostics that still might tell me that I need to spend the $500.

As far as emissions go. I didn't post my emissions score because I haven't actually had them tested. The exhaust is extremely strong-smelling and I failed absolutely miserably 2 years ago. I mean at least like 4x the allowable levels.

We never actually solved the emissions problem last time cuz I took it to a shop to have it fixed and they simply dialed back the mixture so much that the car was hardly running (so I passed). That was the first and only time I will take my car to that shop (Fat City German Motors in Seattle). They charged me a fortune on dead-end diagnostics as well... A $1,500 bill and a car that was running WAY worse than when I dropped it off. They really didn't seem to know what they were doing.

So there you have it. I will report back when I get the Catco cat installed. Hopefully it goes ok and I pass emissions before the end of the month (when my tabs expire!). I will be elated if it solves my rough idle and hesitation problem (which has basically existed for the last 4 years), and satisfied if it only solves the emissions.

Thanks for your help everyone.

Bigpete123 · #8 07-18-2008, 01:29 PM

Oh and Re: the EGR valve. I have definitely investigated that. I would like to save money and do the work myself, but cleaning or replacing a clogged EGR tube sounds like a huge amount of work for a non-mechanic (me) to tackle myself. I don't feel comfortable taking tons of things apart just to access something else... it makes me nervous.

Obviously swapping out the valve itself is easy and very accessible, but I don't even know how to determine if it's malfunctioning.

mr300ce · #9 07-18-2008, 08:57 PM

Here's a secret "they" don't want you to know about testing the mechanical part of the EGR system. (if all is working, remember, the computer is what tells the valve "when" to come on, BUT, the computer is RARELY the problem with EGR troubles).

1. Locate it on the engine (Bigpetes is on the rear end of the exhaust manifold)

2. disconnect the vacuum line on it

3. attach one of your own (bought at a parts store for pennies, 3ft)

4. with your mouth, suck on vacuum line firmly. A good valve's diaphram will hold vacuum. If air keeps coming in, (like a straw) then the valve is bad. = replace valve

5. if valve seems good, start engine and let idle. Apply vacuum again. Engine RPM should drop because you are allowing exhaust gas into the fuel mixture at the wrong time.
This system is working properly. Do it several times to learn how it effects idle, and to feel good that you did it yourself.

6. if engine RPM does not drop , then the tubing and/or ports are likely plugged with gunky egr goo, and won't allow flow.

That may be a job you can do, or not. But you yourself have now tested the mechanical portion of the system.

mpolli · #10 07-19-2008, 12:57 AM

Make sure they give you the old cat. Look at your old one so you know they gave you the right one. 2 reasons: 1) In case there i sno improvement you can sell one of the cats on Ebay or keep as a spare. If it really was bad you can sell it for 100.00 or more to a recycler such as cashforconverters.com etc.

Bigpete123 · #11 07-20-2008, 02:52 PM

Thanks guys for the advice.

Very helpful. I will definitely test the EGR valve in the way you describe mr300ce. That sounds easy enough!

If it turns out the EGR tube is clogged, that's something I'll have a professional fix. But if the valve is bad, it looks like it would be a 15 minute DIY to swap out.

The problem for me with keeping the old Cat is that I live in a 1br condo in downtown Seattle. i.e. no storage space! My wife would kill me if I put that in the middle of our living room!

mpolli · #12 07-29-2008, 01:14 PM

Well.... what happened?

Matt L · #13 07-29-2008, 02:17 PM

Quote:

Originally Posted by mpolli

Make sure they give you the old cat. Look at your old one so you know they gave you the right one. 2 reasons: 1) In case there i sno improvement you can sell one of the cats on Ebay or keep as a spare. If it really was bad you can sell it for 100.00 or more to a recycler such as cashforconverters.com etc.

You can't sell a used converter on Ebay (or anywhere else). You can't even have it put back into your own car.

mpolli · #14 07-29-2008, 03:58 PM

You can sell it for scrap value.

mr300ce · #15 07-29-2008, 11:50 PM

I can't even give you back your cat, as it is considered hazardous waste. Here in Calif, there soon will be no more OBDI cats allowed. All cats must be OBDII certified for replacement on all cars. The price has been going up for OBDII cats.