Codes P0300 and P0302
 

Hello all
I have a 2003 Infiniti G35 Sedan which is throwing the P0300 and P0302 codes. I cleared code twice and they came right back. ( a week before I was getting p0172 I believe it was for 172 but I do know it was for running lean. now 172 stopped and I have 300 n 302.) This 300 302 just happened. I looked up and it says something about #2 cylinder and jumping misfires. Not sure. Now funny thing is car is running fine. Accdelerates fine, no studdering, starts immediately. So yes car is running just fine. But I am sure it is throwing these codes for a reason. I read to check fuel pressure regulator but I cant find it. I found Damper but do not know where the FPR is located. I checked on auto zone to see what it looks like. Read there is one in pump burt picture ofFPR in autozone doesnt look like that pump one. So I am not only lost but confused. Please any assistance and guidance would be greatly appreciated. Imentioned running lean code only ccaues to one of you pros it may help figure this out cause that stopped one day(without repairs) and these two new codes started) Again, Car does operte fine. NO problems at all with driving, idling
Thank You
Hector
dacrew4009@cox.net

P0302 means there is something wrong with the coil pack for the number 2 cylinder, either an open or shorted circuit, since it's running ok it's probably an intermittent problem but the ECM HAS DETECTED A PROBLEM so it probably needs to be replaced.

P0174 is for bank 2 running RICH not lean, this can definitely be related to an intermittently firing coil pack. I would start by unplugging the harness, taking that coil pack out, and inspecting both for any kind of damage. Blistering of the epoxy resin on top of the coil pack, scorching of the spark plug well boot, oil saturation in the spark plug well, contamination inside the electrical harness, wear on the spark plug.

Repair/replace components as needed, clear codes, see what comes back.

I read somewhere about swapping with another cylinder. Before I read your responce I did remove coil pak but changed it with number 4 coil cylinder. Coil looked just fine and no oil on it or in hole where plug is. Looks good. Though I am aware this does not mean it is good. Anyway I swapped number 2 and 4. Put car back together and started car. Drove for 10 minutes and no codes at all. Still runs fine. But I am sure some codewill show up in a day or so. Just want to see if it is still 302 or changes to 304... Once it shows up I will tell all the codes am going to follow your instruction to the tee. Will keep all posted on what is going on with this car problem.

HI
The next day I cleared codes twice and both 300 and 302 came back on immediatly. So I removed and swapped coil pak number 2 and 4. Put car back together. Went for a drive but only 20 minutes and no code.
1/21/19 While driving to store and CEL blinked on off about 5 times in as many as seconds then went off. Got a code P0300 and P0174. I cleared codes again.
1/25/19 Since code on 1/21/19 I have not received any CEL. No CEL at all But code P0174 still shows on reader. NO CEL but reader still shows a code number after clearing. I checked to make sure light to CEL still works and it does. I purchased Plenum and valve cover gasket sets and the coil Paks. Will change all of this anyway. Not sure what cause the CEL of 0300 and 0302 cause since I swapped coil paks the code 302 no longer comes on. Maybe something with connection was loose. I noticed Plenum gasket is metal, do I need sealer or glue to put on these gaskets. Anything else I may need to complete this job? Any suggestions or thoughts will be greatly appreciated,

My suspicion is your spark plugs are old and fouled. I would definitely remove and inspect them, best case is it costs you an hour of your time if everything looks ok. If you don't know when the plugs were last changed you might just buy new ones and replace them all, use the OEM plugs.

Plenum gaskets are 100% reusable, no sealant required. Don't pinch the oil fill neck between the plenums or it whistles like a banshee and will throw a CEL code.

Again, I thank you and hope I am not beiong a pain in theeeee but I need. You have the knowledge I need. Now i did replace all the plugs 3 months ago. I remeber they are what is called for and cost me $8.99 each. I do not drive much as I am disabled so usually at home. I already purchased a new Plenum gasket set. I understand you said they are reuseable. I also purchased a valve cover kit as mine does leak. Figure I will replace all the gasket as I work my way to valve covers and back. Hopefully this will fix the P0174 and 113 I think it is. I will also remove plugs to check and make sure they are fine. (Which they should be if only 3 months old). Don't know what all this code could be from but I feel after doing all this I should be fine. If not then it has to be a leak from somewhere. I thank you for you help. Believe me when I say thank you that I truly mean it as you take time from your day to help someone you do not know. Thanks

Edit: I removed the air intake(long black big hose that leads from air filter to throttle body. ( I only explain as I am not sure if I am using correct name of items) The flap in throttle body has black caked dried oil around inner wall where the rim of flap opens and closes. What would cause this??? Thank You

If it's that thick around the throttle body I suspect you have a clogged PCV valve or hose and are backflowing that air into the intake pipe. There are 3 total hoses, one that goes from the air intake you removed and it connects to the valve cover right below the throttle body. The next hose goes from the actual PCV valve located in the passenger side valve cover up to the middle of the intake plenum. The final hose is at the front of the motor and it connects the two valve covers together.

Remove all 3 along with the PCV valve which unscrews from the valve cover. Shake the PCV valve to make sure it rattles, if not then clean it out with throttle body cleaner until it does. spray more TB cleaner through each hose and make sure it blows freely out the other end.

There is also a chance that you have a problem with the valve cover itself. What can happen is the baffle behind where those tubes connect can get blocked with oily sludge debris so not enough air can pass through, the crankcase pressure has nowhere to go so it blows out a section of the valve cover gasket.

That much accumulation on the throttle body could well be attributed to PCV backflow up into the intake tube because of a poorly flowing system.

I would first swap the coil pack to any cylinder on the OTHER BANK and see if the codes move around.

Next, since you already have the gaksets, dive into replacing the valve cover gaskets, passenger side is very tight and you definitely want to take the mounting bolts off of the EVAP stuff on the back corner so you can move it around. While the valve covers are off spray TB cleaner through the PCV tube welded bungs to make sure there's no blockage.

Since you are reusing your valve covers I STRONGLY recommend you use a small bead of Permatex Ultra Grey RTV around the non-replaceable spark plug well gaskets in each valve cover before reinstalling them or there is a very good chance they will start leaking oil into the spark plug wells. Make sure to give your permatex 25 hours of cure time.

Do NOT work the throttle plate by hand, the electric worm drive gear is easily damaged, plan on getting a plastic bristle brush and bending the head at a 90 degree angle so you can scrub the throttle plate in the closed position. You will use a lot more TB cleaner this way but you run a much lower chance of damaging the thing. I've never taken the electric motor off for cleaning (although I will as soon as I get my hands on a second one) but I have a theory that it comes apart easily and will allow for cleaning of the TB without potentially damaging the electric motor for it.

When you get everything back together it's going to run weird until you perform the idle air recalibration. Make sure the engine is at operating temperature and that EVERY electrical load is turned off including the radio/headlights/AC controller/everything. Only then can you do the idle air recalibration. Get a stopwatch, the seconds counts need to be exact. If you cannot get it to work properly then it can also be reset with a bluetooth OBD2 scanner and the android app Nissan DataScan 2. The pedal dance works though but it does take a little practice, you aren't going to screw anything up from doing it wrong, it simply won't happen.

https://nicoclub.com/archives/g35-35...procedure.html

Personally I would perform ALL the resets from that page, in order, when you are done. Make sure the engine is up to temp for the idle air reset though or it will run VERY badly.

I did swap the coil paks from cylinder 2 and 4. Since I have not recieved code 302. Matter of fact I no longer get any code. The day before I swapped coil paks I was getting 0300 and 0302 before swap. After I swapped coikl paks from 2 and 4 I got a 0300 for a few seconds and then no CEL" at all. Since swapping I get no CEL just a 0174. I left them swapped. I still checked with code reader and get a 0174. But anyway I ordered new valve covers for both sides. Cylinder 1 and 3 has oil in the spark plug tubes. So oil is leaking from covers.
I ordered valve covers a as well. so I will be replacing valve covers and the valve cover gaskets, Plenum gaskets, coil paks and PCV. I will follow your instructions. When I receive the calve covers and all when this is done I will come back with an update on how things worked out. You da man :)
Thank You so much
Hector
2003 G35 Sedan

Ok I gave you a little bad advice earlier, got my codes screwed up.

P0174 is for LEAN not rich, look for a vacuum leak along the pcv hoses, also look for an exhaust leak around the header collector gasket on the driver side.

UPDATE: Replaced valve covers and gaskets Been waiting on parts. Now I am stuck on torgue. I do not know the torgue for the lower plenum to the manifold . and the torque for the upper to the lower (The 6 long bolts) I have read work way up to 70 inch pounds for lower and 110 for upper. Then I read 120 inch for both upper and lower. I also read you have to put oil on the gasket between the plenum and lower manifold. Read this on motordyne. So I am so confused I stopped and hoped you could help me. Please I need all the torques for the Plenum, both top to bottom bolts and the bottome plenum to the manifold. Also need to know if I put oil on the gasket that goes beteewn the Plenum and the lower manifold, The one that is completely under the plenum as ifPlenum is together then there is a gasket under that to the top of engine. Tired and know I am babbling. Been trying to find this.
Thank You

The fsm does not call for oil on the gaskets. As for the bolts, it's a two step torque setting. Separate the bolts in 3 groups according to length and tighten in numerical order

https://cimg7.ibsrv.net/gimg/g35driv...441e37ba4b.jpg

Correction: the two step torque process is for the valve covers. Just get them snug and do a final pass in numerical order
https://cimg5.ibsrv.net/gimg/g35driv...2dfb6f8b2d.jpg

Thank you for your hel;p but I am not sure I understand. Problem is I do not know the proper names of these parts. I will try. The Plenum has an upper and lower part. The plenum is also called upper manifold? The lower part of the Plenum has 6 long shank bolts the connect it to the Lower manifold. There is a gasket between them. No oil here I understand. But I do not know what the torgue is for these 6 bolts. I the past post it says 61 inch pds. for the 18 bolts that connect the upper part to the lower. Buit later in another post you say just snug them down. Can you please let me know if there is a torgue figure for the 6 long shank bolts that connect lower part of plenum to the lower manifold. Also the torque for the bolts both long and short that coonect upper plenum to lower. Sorry for being a pain but your help is truly greatluy appreciated.
Thank You

9 ft lbs. Convert it to inches lbs if you want. I'm saying snug them down before you torque each one. The fsm calls it a manifold, commonly referred to a plenum

There are 3 different length bolts so make sure you match up the numbers to the right spot