Hello, I just want to start by saying that, I do know a little to a fair bit about engines. But, I am by no means a master mechanic lol. So all suggestions and help is highly appreciated...

I have a 2003 Nissan 350Z Base model. A while back it started misfiring. (Sounded like a cammed out muscle car.) So, I took it to AutoZone, had them hook it up, and I was told that the the camshaft positioning sensors were bad. (Bank 1 & 2.)

I bought the sensors, and new spark plugs at AutoZone, and replaced them myself. (I can't remember what brand the sensors were.) And miraculously, my problem was fixed...... For about a month.

Around a month later the car started doing the same thing. So, I took it back to AutoZone, they hooked it up, and tell me that it is now throwing different codes. One was random misfire, another was, 02 sensor downstream bank 2, and the last was for the knock sensor (P0327)

I took the car to O'Reilly's, for a second opinion, and their OBD2 scanner gave the same codes. I bought a knock sensor, 02 sensor, and new plenum gaskets from O'Reilly's. The guy who sold them reassured me, over and over that the P0327 code was for the knock sensor itself, and not the sub harness. I wanted to replace it while I already had the engine took apart but, the guy at the auto store told me that would be a waste of time, and money. And they don't sell that harness there for some reason...

First, I pulled the upper and lower plenum apart, and the intake manifold. I managed to remove the intake without removing the fuel injectors. I replaced the knock sensor, and put everything back together with all new gaskets, and torqued it to spec. I then did an ECU reset, and cranked the car. No change at all.

A few days later I replaced that 02 sensor. I ended up returning the one from O'Reilly's and buying an NTK brand that was the exact same band and matched the one I took off of my car perfectly for $10 cheaper on Amazon. And, also I didn't have to splice this one. Like the, universal Bosch that I bought from O'Reilly's..... <--- (Can you say rip off... Ridiculous!)

After replacing the 02 sensor, I cranked the car, and the CEL went off and stayed off while idling. (It was still missing but not as bad, it seemed.) The next day (today) I drove it for about 25 minutes or so, and then CEL came back on (within the first quarter mile) and was flashing and it mis-fired the entire drive.

Before replacing the 02 sensor, the car would miss, and the CEL stayed on and flashed for the most part. But, usually while driving after a while the car would stop missing, the check engine light would go off completely, and would regain power..... For a little bit, anyways. The problem usually came and went everytime it was drove. (This was odd to me.) But, after the 02 change, it constantly missed and the CEL flashed the entire time the car was moving. (The CEL stopped flashing only when the car was just idling at a red light, or something)

Sorry about the long post guys.... I just wanted to be as clear as possible about everything that is going on and what all I have tried. I am at a loss, and tired of spending money on parts that doesn't help at all. Any suggestions or advice would be great, thanks!

 

I had a problem with aftermarket Camshaft sensors, i didnt have the same misfire problem you did but my car would take a second to startup and would randomely go limp while driving for a few seconds, After replacing the camshaft sensors with ones from Oreily's it fixed the car going limp while driving, but did NOT fix the car from taking a second to start up. After about a week of dealing with this and reading up on some other stuff, sometimes these cars do not like non OEM camshaft sensors and they do weird things, So i went on rockauto and bought the OEM Hitachi replacements and i put them about a month ago and have had 0 problems since, I would wait and see what other people think you should as there are tons of people on here that know 10x more then me, before buying the OEM sensors but thats just what happened to me

 

Also i recently did my valve covers and hooked the coil pack harness up incorrectly and my 3.5 Nissan sounded like a built track car aswell lmfao. Make sure you have all the coilpack's plugged into the correct order.

 

Yeah, I have read where quite a few different people have had problems with non OE camshaft sensors. Unfortunately I read this after I bought and replaced mine with the AutoZone brand.....

The worst part is I found OE replacements online for just $25 more than I paid for the knock Offs.

Something else I didn't mention is when I pull out my #5 coil pack it has some oil on it. The rest are dry except for that 1. I would replace the valve cover if I knew it would fix it. I wish you could replace the coil pack seals (or whatever they are called) without replacing the whole valve cover.... I think it's ridiculous to have to replace that entire expensive *** cover just because one seal is leaking....

 

Is there oil in your plugs ? If so that can cause a misfire aswell thats why i just replaced both my valve covers actually.

 

Both valve covers are like $55 shipped from ebay.
You could clean the oil off the wire/plug and if misfire goes away then you know it's the oil causing the issue

 

I actually just took it to a garage and had a diagnostic ran on it. The guy said that I needed to replace the valve cover and the the number 5 coil. Which is what I suspected. According to him that should fix it.

And he also said that they would only charge me $612 to replace the valve cover. Not including the new coil pack. What a great deal.....! Uh, no thanks. Im gonna tackle that bad boy myself.

 

This is more or less what my plugs look like. I'm not sure what you meant by "is there oil on them?" I know it doesn't look great but, honestly I thought they didn't look too terribly bad. Any opinions on it?

 

Have you had any problems with those valve covers yet? I've found plenty of ones like you mentioned on eBay and Amazon but I don't think I found a cheap one like that, that had a single good review. Everyone had said that the gaskets and/or grommets for the coil packs blew out within a week....

I really hate to pay between $100 and $200 for just one side. But, if the cheaper ones are all but guaranteed to blow out no sooner than they are put on, I'd rather pay the extra cash. At least, Id be pretty confident that I wouldn't have to do all that work more than once....

 

Haven't bought them, but I would if I needed to. Why not just pull covers and use 1-min gray rtv from the tube?(permatex)

 

I have thought about this. But, from what I've looked up online, that would end up being a hit or miss on whether it holds or not. And to be honest, once I pull it and get it replaced, I don't want to have to do it again....

That might sound lazy of me but, I hate taking the plenum and stuff with gaskets and torqued specs apart any more than I have too....

I think I've decided just to spend the extra money and get A new one that at least meets OE specifications. Just to be sure.

It's a bit ridiculous that, Nissan couldn't have made those valve covers with replaceable grommets. I guess the guy who came up with that idea, must have been the same a**hole that designed that retarded dip stick for the oil pan..... I mean who said, "you know what this dip stick needs....? A bunch of bends, and curves, that's what!"

 

Im About to buy the Valve Covers, gasket set and coil pack (6), and torque wrench from Amazon ($230) and do it myself. I am having the same issue on my 2004 350. I'll probably do the work this weekend. I'll keep yall posted.