Loss of power - is my catalytic converter bad?
09-14-2006, 05:27 PM
#1
Burning Brakes
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Loss of power - is my catalytic converter bad?
After a few spirited runs approaching the redline, the engine looses power, and starts 'pur-pur-pur..', for a few seconds. It actually doesn't feel strong above 5 krpm at all. Something also rattles above 5 krpm.
I'm thinking the catalytic converter is clogged, and when it heats up at high rpm it temprarily gets clogged more (is it possible?), creates more backpressure. The rattling might be from broken pieces inside the cat.
Does my theory make sense?
FYI: I've had the car for about 60 k miles, and this might be the original unit.
I'm thinking the catalytic converter is clogged, and when it heats up at high rpm it temprarily gets clogged more (is it possible?), creates more backpressure. The rattling might be from broken pieces inside the cat.
Does my theory make sense?
FYI: I've had the car for about 60 k miles, and this might be the original unit.
Last edited by Stan944; 09-15-2006 at 10:40 AM.
09-15-2006, 11:05 AM
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Burning Brakes
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The only way to really tell is to pull it and have a look. You should be able to see light through the catalyst honeycomb.
Your symptoms could be a number of different things though - ignition and/or fuel related. Check out FR Wilk's site (http://frwilk.com/944dme/) about the early DME. He does a really good job of explaining the system and how and what the sensors contribute (suprisingly little overall, except the AFM and TPS...)
If it were me, (not that I advocate tampering with the emissions equipment) and I went through the trouble of removing the converter, I'd bust the catalyst out and put the empty housing back in.
Your symptoms could be a number of different things though - ignition and/or fuel related. Check out FR Wilk's site (http://frwilk.com/944dme/) about the early DME. He does a really good job of explaining the system and how and what the sensors contribute (suprisingly little overall, except the AFM and TPS...)
If it were me, (not that I advocate tampering with the emissions equipment) and I went through the trouble of removing the converter, I'd bust the catalyst out and put the empty housing back in.
09-15-2006, 11:34 AM
#4
Burning Brakes
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thanks John.
FYI: I just put new spark plugs, wire, distributor cap/rotor, and air filter. It made a big improvement at lower rpm, but above 5 krpm is still bad.
I'm thinking of getting a Magnaflow cat installed, but I don't want to waste money if this won't make much difference.
I heard that the the lifetime of a cat is under 100kmiles. Is it true?
FYI: I just put new spark plugs, wire, distributor cap/rotor, and air filter. It made a big improvement at lower rpm, but above 5 krpm is still bad.
I'm thinking of getting a Magnaflow cat installed, but I don't want to waste money if this won't make much difference.
I heard that the the lifetime of a cat is under 100kmiles. Is it true?
09-15-2006, 11:48 AM
#5
Cast Iron Man
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Is there a lot of heat comming up into the cabin? My clogged cat made it so I didn't have to use the heater in cold weather.
I welded in a bypass pipe and my car has never been happier!
I welded in a bypass pipe and my car has never been happier!
09-15-2006, 12:26 PM
#6
Burning Brakes
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Originally Posted by SD Porsche Fan
Is there a lot of heat comming up into the cabin? My clogged cat made it so I didn't have to use the heater in cold weather.
I welded in a bypass pipe and my car has never been happier!
I welded in a bypass pipe and my car has never been happier!
Steve, did you have a similar power loss after reving it up?
How did you know it was a clogged cat, what were the symptoms in addition to the excessive heating?
09-15-2006, 12:45 PM
#7
Cast Iron Man
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In addition to the tunnel getting warm the motor just seemed "bottled up". Not very free reving on the road. I was also only getting about 7psi of boost and there was a resonating sound in the exhaust.
Welded in a straight pipe and it was like a completely new car. Instanly had the stock 11 psi of boost, no excess heat in the cabin and it pulled to redline like a freight train! The guy who cut the cat out for me said that it was about 75% blocked. My O2 sensor was also fouled. My guess it that the PO had been running cheap gas for a while and that was the genesis of the issue.
Welded in a straight pipe and it was like a completely new car. Instanly had the stock 11 psi of boost, no excess heat in the cabin and it pulled to redline like a freight train! The guy who cut the cat out for me said that it was about 75% blocked. My O2 sensor was also fouled. My guess it that the PO had been running cheap gas for a while and that was the genesis of the issue.
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09-15-2006, 01:03 PM
#8
Burning Brakes
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OK, I think I should get a new cat.
If anybody else had a similar experience, please post it.
I don't have welding gear (nor the skill), so I'm not sure if it's pratical to install a test pipe in my case. Although relatively easy to cut out the cat, test pipe installation with clamps might be tricky, and could leak gases to the cabin.
If anybody else had a similar experience, please post it.
I don't have welding gear (nor the skill), so I'm not sure if it's pratical to install a test pipe in my case. Although relatively easy to cut out the cat, test pipe installation with clamps might be tricky, and could leak gases to the cabin.
09-15-2006, 01:10 PM
#9
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get it up to temp and have someone hold the rpms up- see how much exhaust is coming out and if it smells hot...you should have good flow. also the header could potentially get red hot and crack if that is like that too long so get it up to temp at night and see if the header is glowing alittle...Definitly a cat in that case.
