Expensive Mercedes Repair - Advice?

[Porsche_monkey]

I have a 97 Mercedes E420 with under 80,000 miles. Nice car, I've had it about one year with no problems. I like and I'm going to keep it a few more years.

For about a month it has run rough and the 'check engine' light has been coming on. Last week it started to misfire (lean) and it ended up needing a new intake gasket which I thought was the end of the problems.

After that repair it still ran poorly and now the mechanic tells me the right hand cat is plugged.

So I've likely spent $750 on the intake manifold, now a factory cat is $1,250 plus labor.

Option1 would be knocking out the contents of the cat as a 'temporary fix', although he claims the OBDII will turn on the check engine light with one cat missing. I'm not convinced this is true. And I have 18 months before my next emmissions test, although I suspect this car would pass with one cat.

Option 2 is an aftermarket cat, which he says is about $400 cheaper, but he says they sound like crap compared to OEM.

Option 3 is to either buy a $100 cat and adapt it to fit the car myself, using the ends off the old cat, or take it to a cheapy muffler shop and get them to do the same thing. I'm guessing I could do this for between $100 and $250 total. Again, it may not sound like it used to.

My inclination is to knock out the cat and drive it. If it has too many OBD codes I'll go on to option 3.

I feel a bit bad having the mechanic diagnose the problem but not having him fix it, although he did do the intake gasket work. Another $1,500 in parts and labor seems excessive to me, hte car is only worth about $12,000.

Anyone have any brilliant ideas? Is there another option I should consider?

[island911]

My opinion is your mechanic is likely more of a parts changer than a true problem solver.

Take the cat off and look to see if it's plugged -- I seriously doubt it.

[Porsche_monkey]

Actually, I think he's pretty good. I tried for several days to resolve the problems with this car, but it is too complicated for me. And my wife doesn't want to wait for me to fx it, she wants her air-conditioning back.

He put it on the smoke machine and found the intake leak immediately. (When I was looking at the car I could hear a leak, but I couldn't find it, otherwise I would have repaired it myself. )

When he found it still ran poorly after the intake repair he checked the cat temperatures with the car running on the hoist. He says the left one was about 250, the right one was over 400. He says he disconnected the cat and the car ran fine. I assume this is true, because he was pulling the exhaust sytem off the manifold when I dropped by Friday.

I am 90% sure he is correct in his diagnosis.

[Shaun @ Tru6]

Let's assume the cat is plugged. I don't know anything about them, but why wouldn't you just soak it in solvent to dissolve deposits?

[nota]

cats over heat and semi-melt if too rich/lean too long
no solvent will fix a plugged cat
check by comparing flow volume of gas out each side
by blocking with a piece of cardboard and seeing how much pressure is coming out thru the tailpipe
the fix is to cut the out pipe incert and beat the guts out of the cat with a tire-iron and let the chunks blow out then reweld
that will pass a visual inspection

any cat of about the same size flow should work
1200 for a 1/2 V8 cat is NUTS
there is nothing special about M B or even porsche cats
just over priced thats all
get a unit for a ford or chevy hotrod for desent flow at a desent price

1200 should buy a whole oversized system inc headers to tail pipe tips not one cat!!!!!!!!!!

[johndglynn]

Isn't there a thing on E210 Mercs with the hose into the MAF sensor being blocked/cracked that can lead to this sort of problem? Have you searched Benzworld?

Might not be it but worth a search if you haven't already.

[Porsche_monkey]

Yea, I agree with the price comment. OEM is not an option it is a ridiculous price.

But the sound is determined by the shape, so it will sound different. Not that I really care.

[osidak]

You can get a generic cat for the car for $75 shipped or a direct replacement for $395 shipped (pm for supplier as I do not want offend Wayne)

My dad currently has a 97 E320 (since new) and this is the car that finally broke the camels back - He will never own another MB and he has been driving them since 1968 and even worked for them as a designer. This car has been pure junk

Good luck

[nota]

Wayne both lumps are cats or is the front the cat
and the rear lump a muffler ???

and yes the germans are very bad on including extra pipes
and very over pricing the lot

as a hotrodder I always think aftermarket speed equipment esp
if cheaper and better then stock parts as most are
even if a swap from an other car is needed

remember Dr P started hot rodding VWs

[Porsche_monkey]

I think only the front piece is a cat. There is one per side.

I am hoping this is a one off problem, the car has been pretty good up until now.

I am thinking of buying the $75 piece and using the inlet and outlet from the oem cat to make a replacement. I can weld it myself, it will be fine.

When the cat on my RSA went out, I got lucky and got the cat off the first RSA for $140 on ebay, he said it only had 2k miles on it before it came off and the RSA went full race. The next smog check comfirmed the 2k mile estimate. 964 cat from Porsche was something like $1600 IIRC, ouch.

[sewell94]

i do alot of performance work and we run across this issue alot. You could gut the cat, and buy an o2 simulator for the secondary o2, they are about 50 bucks, also another cheap fix that works on most cars is to buy some smark plug anti-foulers and drill it out so the o2 fits in, the o2 recieves less air flow/heat from the exhaust so it thinks theres less emissions, sometimes they work sometimes they don't, but they're like 7 bucks from your local parts place, so they're worth a try.

[Porsche_monkey]

So the absence of the cat will cause problems? How does an O2 simulator work? Does it provide a set voltage to the computer?

[osidak]

gutting the cat will cause you to throw codes as the o2 sensors will not see the "clensed" exhaust anymore

the simulators are noting more than something to move the o2 sensor further from the exhaust in the attempt to avoid throwing codes

Not sure of your emissions testing in Canada but in my state if your have a CEL for anything emissions related your car will fail inspection

[ChemMan]

Originally posted by johndglynn
Isn't there a thing on E210 Mercs with the hose into the MAF sensor being blocked/cracked that can lead to this sort of problem? Have you searched Benzworld?

Might not be it but worth a search if you haven't already.

That pipe being blocked or cracked will likely kick out a P0170 code. The bad MAF itself will kick out P0170 and/or P0173. Most likely both.

[sewell94]

Well there are 2 types of simulators, the mechanical kinda, basically like the spark plug fouler trick(which does work on some vehicles), and electronic ones, that actually plug into wiring harness and take the the place of the secondary o2, there only a few wires, which makes it very simple to wire up. They give a certain voltage to the ecu just like a secondary o2 to make the ecu think there is a functioning cat.

[Porsche_monkey]

http://forums.evolutionm.net/showthread.php?t=114931

Here is the O2 sensor de-sensitizer. I guess I'll try this if I get codes with the punched out cat.