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Discussion Starter · #1 ·
Bought a 2005 a month or so ago. Guy said it had a miss but drove. Went to pick it up and after getting on the interstate, I quickly realized it was worse than a single misfire. The closer I got to home, the more power it lost. By the time I pulled into the driveway, it was at an absolute crawl. I didn't even have to turn the truck off - it died.

No obvious noises, just a spit and sputtter that got continually worse. Now it wont start, at all. Code scanner threw a P0300.

I pulled the plugs and they definitely looked fouled out, but i also found a receipt from a week before I purchased it for new plugs and labor to install from a local garage. Bought a coil pack and installed in multiple cylinders to see if I could get it to start - no luck.

Has anyone had this problem? I've searched and searched and haven't found anything remotely close to what sounds like what I'm dealing with. Please help!

-Heck
 

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Not to pile on you but it's amazing how many stories I hear of people loosing power rapidly but they continue to drive it until it absolutely dies.

The problem could be a lot of possibilities. How many miles are on it? First thing that popped into my head was your cats, they could be clogged up - they go bad all the time on these things but I don't know if that would foul your plugs tho. Or it could be an intake manifold leak. Or it could be a head gasket (not likely unless you're smoking and/or loosing coolant), could be bad O2 sensors.....
 

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Discussion Starter · #3 ·
You're 100% correct about the stupidity it took to keep driving. No excuse - I could've had it towed. It has 170k on it.

Planning to climb under it tonight and see if it's possible to saw them off and take a peak. Thanks for the idea - it makes the most sense.

-HECK
 

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When I had a plugged cat the brand new spark plugs I had in were totally black by the time I figured it out a few days later.

Using a rubber mallet you could do a quick check for pieces rattling around.
 

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You're 100% correct about the stupidity it took to keep driving. No excuse - I could've had it towed. It has 170k on it.

Planning to climb under it tonight and see if it's possible to saw them off and take a peak. Thanks for the idea - it makes the most sense.

-HECK
Only reason I pile on is (well, I'm a jerk for starters) is I literally have 3 friends who did the same thing only to lock up their motor over something minor. One guy trashed his engine by running it out of oil. He put a hole in the oil pan and rather than try and do a trail repair he drove it home thinking he could out run the leak. He made it 8 miles before it seized (it was a 45 mile drive home). Another had symptoms like yours - gradual loss of power until it let out a short squeal before it too seized. Never did find out what happened but when he pulled the dipstick after it seized it was bone dry. When he dropped the oil pan there wasn't a drop of oil in the damn thing. He just drove it until it quit before even checking the oil.

Removing the cats is not that difficult, it's just a PITA getting to all of the nuts. You have to unbolt both flanges (duh) but also undo the other side to slide the downstream exhaust back enough to remove the cats. Some guys have had luck with getting the studs from the exhaust manifold to come out, which makes it unnecessary to unbolt the downstream exhaust system, but I had no luck. I had one stud that wouldn't budge, so I had to loosen things, but it wasn't a bid deal, maybe an extra 20 minutes. By sawing them off, you will still have to remove the flanges so you're better off just removing them. It would be tricky to get a saw up in there anyway.
 

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Its most likely plugged cat or cats. P0300 is common with that issue. Also yes - it will foul the plugs - the exhaust crud has nowhere to go.

DO NOT START IT AGAIN (yes I am yelling) until you pull your cats and verify. If you haven't already killed it. Lets hope not.
 

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Sawing them off doesn't make it any more difficult to replace them. It's a wasted step - you still have to get in there and unbolt the flanges, so what's the point?
 

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I guess it depends on where you cut them.
I have seen people cut off flanges and all then they have to get new flanges welded on just to install new cats.

So.... If you cut them off don't cut the flanges off.
 

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Discussion Starter · #10 ·
I appreciate all the help. I definitely heard some rattling around in them using a mallet. Going to order some now, replace the plugs again and hopefully start it up. My fear is that I put the new cats on just to find out I melted a valve or something like that. If so, I guess I'll be making someone a pretty good deal on a truck that needs a motor!

-Heck
 

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It may not be a bad idea to take them off. Check that it starts before ordering parts. Since the xterra has four it can get intense.

You can search around this site for more details but a probable cause is that the first cat on one or both banks comes apart and the pieces from that plug up the second cat. This next part is sad. If the cat is indeed coming apart, you must pray that the engine didn't suck any pieces into the combustion chamber.
 

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If your rear cats are plugged, just hollow them out instead of replacing them. They are not monitored by the system in any way, they are just a redundant cat to handle any pollutants that make it past the primaries. The computer will never know if they're there or not. But replace them if you care about pollutants I guess.
 

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Yep, I agree with Tlrtucker. Pull your cats and gut them. Reinstall and see how things run. You will get codes for emissions - P0430 and P0420 but the truck should run fine. The most likely symptom from having permanent damage due to the imploded cats is oil burn - usually more than 1 quart per 500-1000 miles - so change the oil - make note of your oil level - and drive for a thousand miles to see where your at. All if this will only cost you your time and one oil change. If everything is looking good just order new cats at that point.
 

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Yep, I agree with Tlrtucker. Pull your cats and gut them. Reinstall and see how things run. You will get codes for emissions - P0430 and P0420 but the truck should run fine. The most likely symptom from having permanent damage due to the imploded cats is oil burn - usually more than 1 quart per 500-1000 miles - so change the oil - make note of your oil level - and drive for a thousand miles to see where your at. All if this will only cost you your time and one oil change. If everything is looking good just order new cats at that point.
You will not get any codes by deleting or hollowing out the rear cats. They are not monitored by anything.
 

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You will not get any codes by deleting or hollowing out the rear cats. They are not monitored by anything.
He was referring to hollowing out both if the fronts were in bad shape. Usually, the secondary cats are plugged up with the particles of the broken up innards of the primary cats.
Just unbolt both the primary and secondaries and have look. will be obvious what's wrong when you can look inside if that's what it is.
 

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He was referring to hollowing out both if the fronts were in bad shape. Usually, the secondary cats are plugged up with the particles of the broken up innards of the primary cats.
Just unbolt both the primary and secondaries and have look. will be obvious what's wrong when you can look inside if that's what it is.
I was just clarifying my dood.
 

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You will not get any codes by deleting or hollowing out the rear cats. They are not monitored by anything.
While that is technically correct - I was assuming that his front cat imploded into his secondary cat - hence the front cat may already be "hollow". If not, all the better.
 

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Discussion Starter · #18 ·
Alright, so you guys are the best. Went to pull the front cats and sure enough, one was hollow. The rear cat had caught all the crap from the front one, so I skipped a step and ordered new front cats.

Knocked all the crap out of the rear ones and reinstalled. Put the new cats on, replaced the O2 sensor related to the only engine code left and DONE!

I didn't realize how much power the truck had because if you recall from previous post, it failed on the drive home.

Either way - you all fixed it and potentially saved me from damaging the engine any further!

Forever grateful,
-Heck
 
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