My fiancé has a 2004 with the 2.5 and 166k, that hasn't ran in several years. She told me it just wouldn't start one day. Had it towed to the house today. Jumped it with my battery pack and it started right up to our surprise. I pulled 3 codes, downstream/upstream O2 sensors and a misfire in cylinder 4. While I had it running, you could hear the miss and an exhaust leak. The exhaust leak is on the the flex pipe after the first cat, and the exhaust smells VERY rich. After some digging, I found that the first cat is known to fail, and in some cases sucking debris back into the motor causing catastrophic failure. That isn't the case, but I'm pretty positive the cat did fail.

I've put together a parts list of things that we will need to get the car back up and running. It's at about $1200 right now. Some parts won't be needed, and of course I'll have to order more. I plan on doing most of the work myself, however I will have to take it to a shop for some. I'm already in it $400 with the tow bill, new battery oil and a few other things. My question is what would you do? I wanted to sell it after I got it running, but we will end up losing money (the body is in rough shape). We could keep it around and use it to run small errands, maybe a daily driver for me to save on gas instead of my truck, or donate it.

$1200.00 is lots of money. For a few hundred I wouldn’t bat an eye at fixing it and driving it or selling it for a profit.


Do you absolutely have to replace the cats? I’m thinking deleting them would be cheaper. I’d hollow them out, and use the spark plug decoupled trick for the rear O2 sensors.


If they get thieved by methbillies joke is on them.

since it sounds like you don't really need the vehicle and a 2004 is pretty old especially since you said it has a rough body and you seem like an adult that would drive a newer vehicle in better condition.

I would sell the vehicle as is right now and try to recover my 400 bucks

The first cat is also the exhaust manifold. The 2nd cat is attached to the flex pipe that has the hole in it.  At east one of them is already hollowed out

This is what I'm leaning towards. The vehicle is sentimental to my fiancé so it's ultimately her decision. She was excited that I got it running today, I hate to tell her it's mechanically totaled in the morning.

If the car is very sentimental to her, fix it and keep it regardless of the cost.
I talked my wife into donating her worn out 1977 Corolla 20 years ago and have regretted it since then. If I had known the sadness it caused her I would have sunk thousands into restoring it and would still have it today.
Women seem to get far more emotionally attached to their rides than us guys.

Whoops double tap.

I would ditch it. 04 Altima isn't worth the money or hassle. Cut your losses.

1200 bucks plus labor for a 20 year old Nissan sedan in any condition?
Hard pass for me.

Throw a new coil in it, if it runs and drives somebody will buy it for 6-800 bucks
Vehicles are a bad enough investment forget any sentimental crap and move on. It's just a car no matter who owned it. If it meant so much to somebody how did get in the condition it's in?

I wouldn't just assume it is the cat. Replace the front O2 first, clean the MAF if it has one, air filter, check for intake leaks, etc..

I changed that out so it’s not that hard to do. Aftermarket piece I got online.

Have something ready to get the bolts out where it connects to the exhaust. They’ll be rust.

I would figure out the misfire before you spend much more on it. An exhaust leak or bad cat doesn’t create a misfire in one cylinder.

Sucking a piece of cat back in and bending a valve or smashing the plug shut does…

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https://www.1aauto.com/content/articles/can-bad-o2-sensor-cause-misfire

A random misfire, since the mixture is skewed either rich or lean. A dead miss on cylinder 4 isn't coming from a bad O2 sensor.

Diagnose the misfire and go from there. Swap coils, swap plugs, swap injectors, and check compression. If the cores are known to come apart and get sucked in I would suspect a bent valve or damaged spark plug.

Did you miss the part about the hole in the exhaust? The flex piece with the hole is attached to the 2nd cat. Have to replace the whole thing. The O2 codes are likely because of the hole.

The first one seemed really easy, found a kit with gaskets and everything on Rock Auto for about $200. I can easily do the whole system on jack stands, but I'd much rather have a lift. I think the whole system was about $600 through Rock Auto.

I do plan on digging into that first since I've found the hole in the exhaust. I have no idea how well it was maintained prior to my fiancé owning it. I know she did not take good care of it. I suspect the plugs have never been changed and possibly a bad coil.

I initially thought there was a leaking injector which caused it to hydro lock, which is why it wouldn't start, but now I think it was the clogged cats.