Solving the P0300
 

Good to be back on the org! I got back into a maxima for a daily driver and found this steal on a 5.5 6MT up in Dallas. The car has 175K miles, folder worth of maintenance, and was sitting for about a year. Primary purpose of the car is to server as a daily to my FBO Q50 Red Sport. I plan on doing full exhaust, suspension, and wheels for this car once I do full maintenance.

Owner stated the car has no power, mechanic told him the cats are the issue based on the heat + smell of exhaust. I've been searching the forum quite a bit along with the help of friends from my 4th gen days for a guideline on how to tackle these codes. I wanted to record the troubleshooting steps to possibly help other owners out there with this common issue


Started off with the car pulling these codes...
A friend of mine back from my 4th gen days had spare CPS, OEM coil packs that he sent over to me. I also ordered new NGK spark plugs as well in effort to tackle the P0300. I thought I'd start with the CPS, spark plugs/coil packs, then move onto the cats. So far, I have replaced the CPS, coil packs, and spark plugs. The P0300 still remains and the car does not have any power, feels like 3 cylinders. Next step is to drop the cats and gut the cat near the firewall and replace the cat near the Y with a 240SX test pipe I ordered. However, first bolt I snapped. And, the Y-pipe bolt is so stubborn. I bought a torch and will be attempting them again this week.

https://cimg9.ibsrv.net/gimg/maxima....454a5aa12.jpeg
https://cimg1.ibsrv.net/gimg/maxima....b1b202a6f.jpeg
https://cimg2.ibsrv.net/gimg/maxima....719eec209.jpeg
https://cimg4.ibsrv.net/gimg/maxima....486f16b67.jpeg
https://cimg6.ibsrv.net/gimg/maxima....485f722e8.jpeg

I would start to see first if I have spark? Checking for spark signal going to each coil pack and an easy way is using an ole school timing light on the wiring to the coil pack...This voltage in the harness will trigger the timing light...watch the light and see if you notice any misses! This is so easy, it's funny and I've been using this method on coil pack equipped cars for over 20 years. It works!

I'm south of Dallas in H-town and if you ever need support. I think my experience would be beneficial since I have a 2003 SE Titanium Edition Maxima exactly like that!

Cool, good to know. I am in Houston time to time to visit family. You have a link to a reliable light? I learned about the timing light but when I went to look up buying one. They had inconsistent reviews.

Just to add to this thread as I was recently being deluged with just P0300 codes, no other codes and always plenty of power just to make clear the differences in our situations. Replacing the two camshaft (not crank) sensors seems to have resolved my problem - no codes since doing so and its been driven nearly daily for a couple of weeks. Hope this helps.

Have you replaced the ignition condenser? Its wrapped in black tape along the harness.

People keep trying that. I don't think I've seen a successful post on here from it LOL.

Thank you for all the input so far. I am actually dead stuck on removing the primary cat near the y. I've tried heat, days worth of PB blaster, breaker bar, impact, bolt extractor, heat + pliers, and nothing. I am about to get a saw and cut the pipe and check out the cat.

My P0300 was a combination of fouled plugs from oil consumption, bad PCV valve, faulty coil, leaking intake manifold gasket, leaking intake boot.

Update for 01/06:

I was stuck at removing the nuts for the primary cat near the Y. I ordered 2 sets of bolt extractors, portable propane heater, and even more PB plaster. Nothing is working, it's just continuing to round the nut. I have a 240SX test pipe waiting to go in and I was very anxious to see what the conditions of the cat was like. So, what did I do? I went to Wal-Mart and bought a saw. Yes, a saw. I cut it and low and behold...what do we have here..
https://cimg1.ibsrv.net/gimg/maxima....36022535d.jpeg
https://cimg2.ibsrv.net/gimg/maxima....c6affeb2c.jpeg

I let the car idle for a few minutes after I cut the exhaust and cleared the P0300. Idle was at 750ish solid and the car sounded healthy. No stuttering, no misfires. Few minutes later, car was misfiring again at idle. I decided to take the car around to see what the power was like. To my surprise, power was drastically better! Car feels like it has 6 cylinders again. I drove it around for a mile or two and the P0300 cleared! My next step is getting the car back into the garage and gutting the other cat near the manifold. As you can see from the pic, it broke down and filtered down to the main cat under the car. I would rather just have all the cats gone before going forward.

Oh, also picked up a RevUp 6MT Sedan from Houston wednesday night.
https://cimg2.ibsrv.net/gimg/maxima....8a2e24fcd.jpeg
https://cimg3.ibsrv.net/gimg/maxima....c6e14dda5.jpeg

Swapped the 02 sensor, gutted all the cats, fuel filter, CPS, and the P0300 flashes at idle. After taking off for 5-6 seconds, the code goes away and the car feels relatively strong. 0 codes after those 5-6 seconds.


any else ideas?

I ordered bank 2 sensor 1 02 sensor, fuel injector seals, Valce Cover gaskets, new fuel pump, PCV valve. Going to clean fuel injectors while I am doing the Valve Cover gaskets. Car definitely bogs when I punch the pedal and the hesitation goes away after a split seconds. Still feels pretty slow.



Car is now blowing white smoke under full throttle after I gutted the cats. Does not smoke at idle, and coolant is solid along with temp. I don't think it's the headgasket and just the residual soot from the gats being gutted.

They work and as live as I can get watching a coil pack actual miss it's ignition event...I'm here and waiting to look at this car ASAP....

Wow those cats.......you're definitely on top the leader board with that level of disintegration. Piston rings are probably shot. At this point I'd stop tossing money at it. Your best bet at this point is to scrap the engine and do an "hr swap" - toss in an engine from a 7th gen maxima. They have the more reliable 2nd gen 3.5DE engines. 1st gen DE engines have a well documented problem of exactly what you've experienced - front pre-cat disintegrating and the remnants getting sucked back into the engine which cause all sorts of problems. Probably not what you wanna hear I realize..... but you'll be fighting that problem forever, unless you wanna re-build the engine. Sometimes just better to cut your losses and move onto something better.

Fyi, you can get a 2nd gen DE for around 600-650......and if you add up the cost of all the parts to fix your current engine issues it could be a lot less.