Catalytic Converter / Muffler woes........
11-16-2001, 07:41 PM
#1
5th Gear
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Join Date: Nov 2001
Location: Fresno, Ca.
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Catalytic Converter / Muffler woes........
I was told by my Porsche dealer that the cats. on my '86 were shot, and my mufflers were plugged. Had the cats. replaced (they were EMPTY TUBES ! ). I do here some rattling in the rear muffler when I shake the exhaust. The engine dosen't want to spin past 3500 or so....unless I REALLY push it, and there is a missfire/roughness at higher RPM's. If I go over a speed bump, or make a fast,hard turn, the engine spins much more easily.....for awhile. Does this sound like plugged mufflers ? Would all the guts of the converters go down-stream and clog the mufflers ? Can I just have the center muffler cut out ? Then replace the rear one with a factory unit ? Much Thanks for any input
Heres an update.....: Went to a muffler shop, had them remove the exhaust from the converters back. The car drives EXACTLTY THE SAME! Cost me $60 to find out $1600 of mufflers are OK. I highly suggest this procerure to anyone who suspects their exhaust system is at fault.
Heres an update.....: Went to a muffler shop, had them remove the exhaust from the converters back. The car drives EXACTLTY THE SAME! Cost me $60 to find out $1600 of mufflers are OK. I highly suggest this procerure to anyone who suspects their exhaust system is at fault.
11-17-2001, 03:47 AM
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Burning Brakes
Join Date: Aug 2001
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Dan,
You may want to have a backpressure test done just to confirm your suspicion about the muffler being broken to the point of clogging. With the apparent complete failure of your cats, you could have enough junk downstream to clog it all up.
There is/are test port(s) on the downtube from the header to the cats. If not, you can use the CO test ports for the job. Any semi competant muffler shop should be able to do the test. According to any sources I have found, the backpressure should never exceed 1-2 PSI.
If you need a used 86 system, it should be incredibly cheap on the open market (ebay,individual). Pieces often go unsold for under $100. Not the type of thing to buy from the 'big 3'. You should be able to pick up the mids and rear for about $150 ish.
Shipping it is a bigger pain than paying for it. You might also try the Porsche recycler in Sac(Rancho Cordova) or Parts Heaven in the East Bay - Kind of a drive from Fresno, but might be worth it to save on shipping.
If you have trouble finding the stuff, let me know if you have an 86 or 86.5. I think a friend has a set in his pile of 928 parts.
Greg
You may want to have a backpressure test done just to confirm your suspicion about the muffler being broken to the point of clogging. With the apparent complete failure of your cats, you could have enough junk downstream to clog it all up.
There is/are test port(s) on the downtube from the header to the cats. If not, you can use the CO test ports for the job. Any semi competant muffler shop should be able to do the test. According to any sources I have found, the backpressure should never exceed 1-2 PSI.
If you need a used 86 system, it should be incredibly cheap on the open market (ebay,individual). Pieces often go unsold for under $100. Not the type of thing to buy from the 'big 3'. You should be able to pick up the mids and rear for about $150 ish.
Shipping it is a bigger pain than paying for it. You might also try the Porsche recycler in Sac(Rancho Cordova) or Parts Heaven in the East Bay - Kind of a drive from Fresno, but might be worth it to save on shipping.
If you have trouble finding the stuff, let me know if you have an 86 or 86.5. I think a friend has a set in his pile of 928 parts.
Greg
