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  #1  
Old 07-18-2003, 02:56 PM
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Join Date: May 2001
Location: San Francisco
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Catalytic Converter - testing?

How would one go about testing for a plugged or disfunctional Catalytic Converter (California)?

I've had intermittant power loss - see discussion at the following link:

ML320 loses and gains power


and I don't believe that I have fuel pump problems, as I replaced both of them myself approximately 1 year ago.

I am getting some smell from underneath the passenger compartment, but it is more of a sweet fuel smell then a rotten egg sulfer smell.

Is there any inexpensive fault isolation that I can perform on the Cat prior to going to the expense of replacing it?

Thanks in advance for your suggestions.
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1989 260e
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  #2  
Old 07-18-2003, 03:41 PM
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The clogged cats in my travels have not caused intermittent problems.
They would consistently "hit the wall" at a certain speed, and positively slog under load, like when climbing a hill.

Just my results.

I'm sure there must be some sort of vacuum pressure test that can be performed for a positive diag, though I do not know the specifics.

Best of luck.
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Old 07-18-2003, 04:07 PM
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csnow,

Actually, the intermittant problems only occur under constant load, such as in hwy driving or during sustained hill climbs.

I noticed the problem when driving up to Mt Shasta over July 4th weekend, when I hit about 2500 ft in altitute on I-5.
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  #4  
Old 07-18-2003, 05:10 PM
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Unfortunately, the way I have determined a cat to be clogged in the past was to partially unbolt the front connection flange, then test drive to see if the problem went away. A little noisy, and not very 'technical', but definitive!

If your 124 is setup like mine, it is all one piece, so this cannot be done.
Seems to me I saw a post go by on how you can test for this with a vacuum gauge. You might try a search.
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  #5  
Old 07-19-2003, 12:01 AM
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Steven,

You can use a simple vacuum gauge to chrck for restricted cats. Tie in to manifold vacuum. Your idle reading should be around 16-20 inches at sea level. You lose 1 inch of vacuum every thousand feet. Run the engine up to about 3 grand and hold. The vacuum should go in the toilet briefly and climb immediately to a value higher than idle. If it is considerably lower, chances are you have a restricted cat or retarded valve timing. When did you last replace the fuel filter? Have you done a pressure anddelivery rate check?


Good luck,
Peter
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