Clogged Cats: Symptoms, Diagnosis & Pics
07-16-2005, 10:38 PM
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Clogged Cats: Symptoms, Diagnosis & Pics
I've been having issues with my truck lately. If its not the crank sensor, its the valve cover spewing oil everywhere. Well yesterday my truck took a dump and I had to get towed home. I haven't been able to rev my truck past 4500rpm in awhile. I kept getting crank sensor codes, so I replace it. Truck runs fine, not great but fine.
Then it wouldn't rev at all and it didn't know when to shift either. It also felt like it had a 5500stall in it too.
It sounded similar to an old piston engine helicopter and it only would idle at about 450rpm.
desTRUCKtive has been saying it was my cats for quite awhile now. Well he was right! Here are some pics of the passenger cat. The driver's side was bad, but you could still make out the honeycomb structure.
When desTRUCKtive and I pulled vacuum readings off the intake and a red flag when up right away. Only 4-5 in Hg at idle! I guess that explains the hard brake pedal.
While reving it would drop to 0 and then build almost 1psi!!! 
Free boost?....not quite. When the throttle blade slammed shut I saw about 11 in Hg. Damn.
Another red flag was raised when my O2's readings were boucing around like a fat kid in a donut factory.
After I cut them off and POURED out what was left of them, I'm happy to report 11-12 in Hg at idle and over 20 in Hg when the blade shuts. My little 4.8 is rev-happy again!
I recommend doing this vacuum check or having your O2's read if your truck is over 60,000miles and you have a decent sized cam with lots of overlap. Also you can drill holes before and after the cats, then hook up a pressure gauge to see the difference in pressures.
A special thanks and shout out goes to desTRUCKtive and onyx for helping get through this, and putting up with my crap.
Then it wouldn't rev at all and it didn't know when to shift either. It also felt like it had a 5500stall in it too.
It sounded similar to an old piston engine helicopter and it only would idle at about 450rpm.desTRUCKtive has been saying it was my cats for quite awhile now. Well he was right! Here are some pics of the passenger cat. The driver's side was bad, but you could still make out the honeycomb structure.
When desTRUCKtive and I pulled vacuum readings off the intake and a red flag when up right away. Only 4-5 in Hg at idle! I guess that explains the hard brake pedal.
While reving it would drop to 0 and then build almost 1psi!!! Free boost?....not quite. When the throttle blade slammed shut I saw about 11 in Hg. Damn.Another red flag was raised when my O2's readings were boucing around like a fat kid in a donut factory.
After I cut them off and POURED out what was left of them, I'm happy to report 11-12 in Hg at idle and over 20 in Hg when the blade shuts. My little 4.8 is rev-happy again!
I recommend doing this vacuum check or having your O2's read if your truck is over 60,000miles and you have a decent sized cam with lots of overlap. Also you can drill holes before and after the cats, then hook up a pressure gauge to see the difference in pressures.
A special thanks and shout out goes to desTRUCKtive and onyx for helping get through this, and putting up with my crap.
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Have you drove it around town? Mine are going 
from this experience.
07-17-2005, 12:35 PM
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I run Circle K 91 octane all the time. 
It's almost never from the same station 2 times in a row though. My truck runs sooooo much better, you have no idea.
I'm affraid to drive it around town, because I haven't welded the "cats" back on. So I just have two 1ft section of pipe and that's it. It does sound good though. 
I thought cats were supposed to last well over 100,000 miles?!? It seems that's not the case at all. Like I said before, if you're over 50-60K miles, look into this. There's most likely some serious power to be had, or a disaster to be prevented.
It's almost never from the same station 2 times in a row though. My truck runs sooooo much better, you have no idea.I'm affraid to drive it around town, because I haven't welded the "cats" back on. So I just have two 1ft section of pipe and that's it.
It does sound good though. I thought cats were supposed to last well over 100,000 miles?!? It seems that's not the case at all. Like I said before, if you're over 50-60K miles, look into this. There's most likely some serious power to be had, or a disaster to be prevented.