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Discussion Starter #21
And there’s no way I’m paying for the original equipment cats, I’ll definitely do longtubes before i do that. But hopefully the eastern cats will last quite a while, I have other cars so I won’t put THAT many miles on the Xterra. I mostly drive one of my Miatas when the weather is nice and I’m doing a turbocharged gen3 V8 in an 82 C10 short bed.
 

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And there’s no way I’m paying for the original equipment cats, I’ll definitely do longtubes before i do that. But hopefully the eastern cats will last quite a while, I have other cars so I won’t put THAT many miles on the Xterra. I mostly drive one of my Miatas when the weather is nice and I’m doing a turbocharged gen3 V8 in an 82 C10 short bed.
Oh man reading that sentence I though you were about to say you were putting a turbo v8 in the miata!!
 

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Also suspecting a problem with Cats, no power, will not go over 60 kmph. New to an Xterra, bought at auction for cheap, body and suspension looked good, engine and transmission clean and not noisy. Bought cheap so prepared for a challenge. More challenging then I expected. Running okay but not the power I would have expected and very low pressure at idle with engine laboring. Started out replacing oil sensor unit, still dangerously low oil pressure at idle. At RPM oil pressure fine. Suddenly oil disappeared, no visible leaks. Changed oil and watched closely, oil levels maintained. Next day without warning, sudden loss of power, will not go over 60 kmph. Replaced oil gallery seals as low oil pressure at idle, did timing chains and water pump at same time, had oil pump but could not remove old one due to bottom protruding pipe that would have necessitated removing lower engine casing. Started up fine, good oil pressure at idle but still no power and multiple cylinder misfire code. Also showing fuel level sensor code so thought it may be a fuel pressure issue and changed fuel pump. Still no power. With disappearance of oil thought that it may have been a stuck PCV valve that blew the oil out the exhaust, checked and very clogged PCV valve so cleaned and reinstalled. Changed out the plugs as pretty fouled. Started up fine but still no power. Showing a bank 2 O2 sensor code so removed and cleaned. While under the vehicle noticed the primary cats on both sides appeared to have heated, looks like the edge seams are burnt out. The rear cats look okay but I am concerned that if the primaries melted down they may have pushed debris into the rear cats and possibly the muffler. Makes sense that a clogged exhaust system is causing the loss of power. Hoping that no more more damage then the exhaust has occurred. Planning to remove the exhaust system from the headers to the tail pipe and inspect and test air flow piece by piece. If I find the primary cats have melted down and are plugged will bore out, check the rear cats and do the same if necessary. If all runs well will proceed with long tube installation, complete cat delete. My guess is a clogged PCV valve caused the oil to be pushed out the exhaust and this melted down the cats, likely fouled up the O2 sensor at the same time. Does this make sense? Any suggestions on other things to check that would cause this extreme loss of power? I am trying to take the low investment approach and diagnose the issue before throwing more money at the vehicle. If the cat delete does not solve the issue I am going to order a set of 4 computer ECM modules, will make sure that I get the proper match for the vehicle type and features.
 

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had same oil pressure problem at idle and loss of power. later found oil coming out the tail pipe at the rate of 1 quart a day. turns out cats were breaking down to a fine powder problem is when you turn off the engine it sucks the powder in to the engine and rips the rings and cylinder walls up letting the oil blow by turning my first engine into a boat anchor. i am working on my 3rd engine as my second junk yard engine had timing chain failure even thow i had it replaced they never pulled the slacker adjuster pin out.
 

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Also suspecting a problem with Cats, no power, will not go over 60 kmph. New to an Xterra, bought at auction for cheap, body and suspension looked good, engine and transmission clean and not noisy. Bought cheap so prepared for a challenge. More challenging then I expected. Running okay but not the power I would have expected and very low pressure at idle with engine laboring. Started out replacing oil sensor unit, still dangerously low oil pressure at idle. At RPM oil pressure fine. Suddenly oil disappeared, no visible leaks. Changed oil and watched closely, oil levels maintained. Next day without warning, sudden loss of power, will not go over 60 kmph. Replaced oil gallery seals as low oil pressure at idle, did timing chains and water pump at same time, had oil pump but could not remove old one due to bottom protruding pipe that would have necessitated removing lower engine casing. Started up fine, good oil pressure at idle but still no power and multiple cylinder misfire code. Also showing fuel level sensor code so thought it may be a fuel pressure issue and changed fuel pump. Still no power. With disappearance of oil thought that it may have been a stuck PCV valve that blew the oil out the exhaust, checked and very clogged PCV valve so cleaned and reinstalled. Changed out the plugs as pretty fouled. Started up fine but still no power. Showing a bank 2 O2 sensor code so removed and cleaned. While under the vehicle noticed the primary cats on both sides appeared to have heated, looks like the edge seams are burnt out. The rear cats look okay but I am concerned that if the primaries melted down they may have pushed debris into the rear cats and possibly the muffler. Makes sense that a clogged exhaust system is causing the loss of power. Hoping that no more more damage then the exhaust has occurred. Planning to remove the exhaust system from the headers to the tail pipe and inspect and test air flow piece by piece. If I find the primary cats have melted down and are plugged will bore out, check the rear cats and do the same if necessary. If all runs well will proceed with long tube installation, complete cat delete. My guess is a clogged PCV valve caused the oil to be pushed out the exhaust and this melted down the cats, likely fouled up the O2 sensor at the same time. Does this make sense? Any suggestions on other things to check that would cause this extreme loss of power? I am trying to take the low investment approach and diagnose the issue before throwing more money at the vehicle. If the cat delete does not solve the issue I am going to order a set of 4 computer ECM modules, will make sure that I get the proper match for the vehicle type and features.
Sounds like the cats have broken up and plugged up the exhaust (causing no power) as well as sucked cat honeycomb into the engine and scored the cylinder rings and walls (causing all your oil loss, burning into exhaust). That’s probably why it was at auction. Needs a new engine and probably all 4 cat converts.
 

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aFe has replacement cats for $323 a piece. You'd still have to pay for shorties if you are in a carb area so doing Long Tube and eliminating two birds with one stone is cheaper.
No performance gain, but then you can cut out the secondary pipes and put the DT B Pipes in and put bottle resonators on them if you don't want a lot of noise. Then you don't ever worry about the secondary ones going out. I have a heat shield rattle on the passenger front cat that I've given up on fixing/diagnosing.
 

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aFe has replacement cats for $323 a piece. You'd still have to pay for shorties if you are in a carb area so doing Long Tube and eliminating two birds with one stone is cheaper.
No performance gain, but then you can cut out the secondary pipes and put the DT B Pipes in and put bottle resonators on them if you don't want a lot of noise. Then you don't ever worry about the secondary ones going out. I have a heat shield rattle on the passenger front cat that I've given up on fixing/diagnosing.
I think i have the same issue! i cant figure out if its the cat iself(material on inside rattling) or a heat shield but i cant find the heat shield. the thing that really concerns me is that it happens no only at start up( cold exuahst but sometimes at temp as well. I dont want to bang on the cat to hard out of fear that ill actually dislodge whatever is rattling in there and cause it to be sucked up in the engine. but i also dont want to just like it go an eventually have that happen. im currently saving for the timing chain job so replacing the cat is not something i want to do right now. any ideas?
 

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I think i have the same issue! i cant figure out if its the cat iself(material on inside rattling) or a heat shield but i cant find the heat shield. the thing that really concerns me is that it happens no only at start up( cold exuahst but sometimes at temp as well. I dont want to bang on the cat to hard out of fear that ill actually dislodge whatever is rattling in there and cause it to be sucked up in the engine. but i also dont want to just like it go an eventually have that happen. im currently saving for the timing chain job so replacing the cat is not something i want to do right now. any ideas?
Mine only happens around units of 10 on the tachometer and never past 60mph. All the heat shields felt firm on that side
 

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Discussion Starter #33
Cats were definitely dead, this is the driver side, which is the worse one, but the passenger side was starting to go too.



I replaced them (which sucks btw) and cleared the codes. No more O2 codes so that’s good and obviously the cats were totally screwed so I did’t waste my money, but I got on the interstate on the way home and going up a hill I got a flashing check engine light and misfire again. I checked it when I got home with a little Bluetooth OBD2 scanner and sure enough I still have a P0300 code every time the engine is under load. I’m starting to think the two aren’t related and I just got lucky and caught the cats when it needed them anyway.

Any other ideas for a P0300 without a specific cylinder when under load?
 

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Discussion Starter #35
Did you check to see if your downstream cats were plugged?

Have you checked your oil to see if your consumption is up or your rear plugs on either side are showing signs of burning oil?
Downstream cats seemed fine just by looking in the inlet side, I didn’t take them completely off to look at the outlet side.

Oil consumption is zero, I changed it about a month ago and put it right on the dot and about 2k miles later it’s still exactly on the dot. I haven’t pulled the plugs yet, I might do that tomorrow after I double check the rear cats. I’m kinda leaning toward an ignition problem, as it seemed to have started right after I went through an automatic car wash. At least it started the same day. I’m thinking maybe a coil or something got wet.
 

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Discussion Starter #37
Probably whatever is giving you the code is what destroyed the cats, without that fixed you have a good chance of just ruining the replacements. Wish I had more suggestions for you.
I agree in general, but the odd thing is misfire code is new. I pulled the codes when I first got it, which would have been May 30th, and the only two codes in it were P0420 and P0430. Also, the misfire under load is pretty damn noticeable, and I take the freeway to work every week, I work in the car industry, I feel like I would have noticed it.

On June 21st, I went through an automatic car wash in preparation for a road trip, and it kinda stumbled a little bit in the wash. I wrote it off to just a plug wire getting wet and figured it would dry, and I was driving around on surface streets so it wasn’t super noticeable. I noticed it as soon as I loaded up and got on the road, but initially wrote it off as the added weight of a bunch of people and luggage. When the check engine light started flashing on the way back is when I got concerned, pulled the codes when I got home and had the P0300. I never had a flashing engine light or the P0300 up until a week ago.

But I do agree that whatever is causing the misfire can and will damage the new cats, so i gotta fix it, just not sure where to start, lol.
 

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sorry if you've already done it, I cant read 4 pages of posts to check, but i would start by replacing the spark plugs, all of them, see if that solves it, if not the maybe move onto the coil packs, maybe you could get a new coil and start replacing the existing ones in succession and see if the light goes of on any particular one?
 

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Discussion Starter #39
sorry if you've already done it, I cant read 4 pages of posts to check, but i would start by replacing the spark plugs, all of them, see if that solves it, if not the maybe move onto the coil packs, maybe you could get a new coil and start replacing the existing ones in succession and see if the light goes of on any particular one?
I was thinking the same thing, re:spark plugs. It likely needs it anyway, so no big loss if that doesn’t fix the issue. In my experience USUALLY a coil pack will give a cylinder specific misfire, but obviously that’s not a hard and fast rule. I

t’s frustrating because I really need to drive it and do some data logging to see what’s going on with it instead of just throwing parts at it, but at the same time I really don’t want to keep causing a misfire and ruin my new cats.
 

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Discussion Starter #40
Someone in another thread (I’ve been searching and reading non-stop, lol) suggested these coils, though they are showing as not compatible, has anyone used them successfully?

https://www.amazon.com/Ignition-Coils-Nissan-PATHFINDER-Compatible/dp/B00FUT7IP6

I generally don’t cheap out, but if I can’t narrow it down to one coil and have to replace all the coils when I do spark plugs, I would rather not spend $50-75 each.
 
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