Hi to all, new to this forum and Nissan. I have tried endlessly using the search function here to no avail for my particular problem. Sorry for the incredibly long post but I want to be as precise as possible. Here it goes..

I bought a 2003 350Z Track w/ 124k miles at the beginning of February. Did a tune up of plugs, oil (Mobile 1 5w-30 High mileage), and air filter. Car did excellent the first month and then started noticing blue smoke for 3-5 seconds when I started it. It only seemed to do it when it sat for more than a few hours and then it started throwing the P0300 code. Tracked that down to the #4 cylinder. When I pulled the spark plug, the top of the piston looked like it had a pretty good layer of baked on oil. The plug itself was completely fouled and the electrode was literally incased in a hard black carbon like substance. I changed the plug and the mis went away and smoothed out perfectly and within 300 miles the P0300 came back and the #4 plug was covered in black oil and it was back to missing. To try and rule out rings, I ran a compression test and all 6 cylinders dry were 169-172psi with the #4 being the 172! Searched on this forum and even took it to the dealer and both lead me to believe it was the valve seals since it only smoked on start up. Dealer told me once I replaced the valve seals that it should only take a few miles to burn that cylinder clean also. No biggy. Ordered the complete head gasket kit w/ new valve seals. Spent 2 days working on it. Replaced all gaskets, valve seals (using the jwt spring compressor so I didn't have to remove heads and possibly have them planed), also did all 3 timing chains, both tensioners, water pump, pcv valve and serpentine belts. The 2 intake valve seals on #4 had NO rubber grommet left inside.

Got it all back together and I was of course expecting some smoke on the first start up to burn any coolant, oil etc that may have gotten into the cylinders. Smoked blue for about 4-5 seconds and stopped smoking. Let her run for a while then shut it off for the night. 2 weeks and around 200 miles later, it is still smoking for a few seconds at start up and within 2 days of a plug change on that cylinder, the plug is already covered in black oil again it is throwing the P0300 code and it also threw the P0304 code once and I can tell no difference in the black gunky build up on that piston. Doesn't appear to have used any oil at all yet so I'm assuming that it is just going to take MUCH longer to clean that cylinder than the dealer lead on. If I knew it wasn't going to be so easy to "burn the cylinder clean" I would have went on ahead and pulled the heads to clean the cylinders while I was down that far into it.

Is there a way to clean that cylinder out without removing the head? Many people I've talked to have suggested running a can of Seafoam through and a few have suggested getting a spray bottle and spraying light mists of water into the throttle body to "steam clean" the cylinders. I'm saying IF I get the cylinders cleaned out real good and it continues to puff blue smoke at start up, what should be my next plan of action? Valve guides, catch can, thicker oil,???? I'm at a complete loss on what to try next to get rid of the start up blue smoke issue.

Any and all help would be greatly appreciated!!!

 

I've heard people use WD-40 to clean out the cylinders over at the Saab forum. Pull the plug on that cylinder and spray a liberal amount of WD-40 in there. Let sit for many hours put towel around the sparkplug hole and crank the car to force excess WD-40 out.

Make sure you pull the fuel pump fuse or whatnot so the engine doesn't actually start during the cranking.

This prolly works with seafoam as well.

 

I am a huge fan of seafoam. It works great!

Just make sure if you use it you let it really sit in the engine for a few minutes few you crank it back up. With my personal experience with seafoam, after you start it back up, drive it and beat the hell out of the car. It will smoke like hell for a little bit but everything will get out.

Plus its tons of fun haha, at least to me. The amount of smoke is hilarious.

I recently seafoamed my B13 with 200k and although the clutch gave out, it was driving alot stronger post-seafoam.

Good luck!

 

When I first started it up. It should look like this.

 

Sounds like Seafoam is going to be the winner! And if I can get a smoke show like that than I may go on and do my 72 Charger 440 at my dad's farm while I'm at it and charge him for crop dusting! I'll try and take some before and after pictures of the piston plus a couple pics or a video of the smoke shows to send my friend that is an investigator for the EPA!