jfridge92

Okay so I got the battery swapped out. The "new" battery that's only been in the car 2 months already went bad. Got it replaced free with the warranty. FYI, it is 100% possible to swap the battery in an autozone parking lot while holding a 1 year old lol.


I drove the car about 40 miles after installing the new battery, and it only logged 1 misfire on cylinder 3. My "used" oem coils fcom Z1 already arrived today (shout out to them for quick shipping!), so I may try and put those in the 1 and 3 cylinders since those two had the most misfires before I started troubleshooting anything.

I'm also trying to track down a smoke machine to smoke test the evap system. I cant find any leaks with soapy water or carb cleaner, but with the #1 plug looking so lean compared to the other 5, something is going on there.

Also, my cats are rattling, so theres that too lol....

Surfnazi

If you change the plugs look at the sparkplug boots for leaks

jfridge92

The coils on the car all looked perfect visually. No tears in the boots or any charred Mark's that would indicate they'd been arcing. I did add an adequate amount of dielectric grease to each boot before reinstalling when I changed the plugs last night.

jfridge92

Okay, 50th update to this lol! So I swapped the #1 and #3 coil since those two cylinders had the most misfires logged. Just took the car for a decent drive, and drove it really hard and then cooled it down easy on the way back. I also let it idle for about 10 minutes once I got back home since it was having more misfires at idle than while driving. Torque is showing 0 misfires logged on any cylinder, and the car drove beautifully.

I'm going to put about 1,000 miles on it before I call it fixed, but maybe a combo of cleaning the MAF's, TB's, new TB gaskets, new spark plugs, two "new" oem coils, a new battery, and the TB and idle relearn fixed the issue. Most of those items were maintenance any way, so I don't mind that I had to spend money on it, as it would've been done in 15k anyway.

The only thing I'm concerned with now is the oil on the threads of the #1 plug. I'm going to drive the car for a week or so and then pull that plug back out again to see if the new plug has any oil on the threads. Since there wasn't any oil in the spark plug well, and there wasn't any oil on the electrode of the original #1 plug, does that still seem like a valve cover gasket leak? I always thought on VQ motors that there'd be oil in the spark plug well if the VC's were leaking. Thoughts on that? Or is it normal to see that amount of oil on a plug after 85k?

jfridge92

Well, it doesn't seem like plugs, the two replacement coils, cleaning the TBs or MAFs fixed the issue. The car is running better, but I am still logging misfires on the car, and it does noticeably shake at idle inconsistently. If I rev the car in park, it stumbles a bit coming back down around 1500rpm as well, as if it's missing on decel.

I'm working on building a smoke tester to see if I can find any evap leaks, but I'm not sure that the car is running lean or rich enough to say a vacuum leak or fuel delivery issue is the cause.

I've been doing some data logging, and my AFR is steady at 14.6ish under minor driving. Full throttle it does go to around 11 to 11.5. The STFT is hovering around -1 to -5, and the LTFT is staying around -5.47, and I have seen -6.4 at the highest, so it isnt running super lean like I'd expect for a vacuum leak (actually seems to be running on the rich side, but within what I would consider normal range).

At this point I'm going to try smoke testing the vacuum system for leaks, and am waiting on a fuel pressure setup from Z1 to arrive so I can get a fuel pressure gauge on the car to confirm. The car does not have any pending codes, and hasnt thrown p0300 again, but it is definitely still misfiring per the individual cylinder misfire counts. Bank 1 is still the primary offender, but I am getting some misfires on bank 2 occasionally. Any other suggestions to check? Could this be a cat issue?

jfridge92

Okay, so I built a DIY smoke machine (I will make a write up in the DIY section for those interested). I just checked over the G for vacuum leaks, and I do not have any visible intake leaks with the smoke test. So, at this point, I am a bit lost as to what to check next.

I am still getting misfires, but they are random and extremely intermittent (like 5 total misfires on different cylinders every 2 or 3 drive cycles). My fuel trims are showing the LTFT now sitting between -7 and -10. The STFT's do seem to fluxuate between rich and lean as expected, but usually do not exceed +/- 10 except under decel, which they then spike extremely lean which is normal on this car from what I understand.

With the misfire being this intermittent, it's been hard to determine what's going on, because it jumps from cylinders, and does vary between bank 1 and 2. Any other thoughts since vacuum leaks are ruled out?


Also, could someone confirm what voltages the upstream O2 sensors should be flipping between? On OBDFusion and Torque, both apps list the upstreams as wide-band O2's. Mine usually sit around 2.2v and will fluxuate between 2.2 to 2.8, occasionally dropping down to around 1.8v. Is this normal range for these? Neither upstream O2's seem to be lazy, they flip around pretty consistently. The downstream O2's seem to sit around .8v or so, which I think is about right once the car is in closed loop.

crookncastle

looks like you got oil going into the combustion chamber. is that sludge on the ceramic near the electrode? as for the ignition coil i believe the oem coils are made by hitachi. i believe hanshin is some made in china aftermarket part. its also possible the coil is faulty and not giving a strong spark and somehow the crud built up on the ignition coil as a result of a weak spark.

jfridge92

No sludge on the tips of the plugs at all, that was just the way my flash reflected off the metal of the plug. The OEM coils that Z1 sent me also have Hanshin stamped on them, so I'm thinking the one's in my car were original.

At this point, the car has been running fine for about 500 miles since completing the tune up. I'm still logging a few misfires on my logs, so just to be cautious, I'm going to pick up an oil pressure test kit from harbor freight and check my oil pressure. My car is a 2013 so it shouldn't have any issues with the oil galley gaskets, but I have no clue how well it was maintained for the 60,000 miles it was driven before I bought it, and it'll give me more peace of mind to know that isn't causing my misfires. I haven't gotten any pending codes for p0300 again, nor a p0011 the other code that pops with the galley gaskets, but it'll be nice to know I'm still okay, and to check it periodically when I do oil changes. I may also add an electronic pressure gauge down the road too. I'll post up the results once I get my kit. I'm also going to send off an oil analysis to blackstone to see if there's anything there.

crookncastle

oem coils are not hanshin. whatever z1 sent you are aftermarket coils so i wouldn't put much faith in its quality. as for oil pressure causing misfires that is not possible. misfires has to do with engine combustion and oil pressure is not part of the combustion process. oil pressure is the result of combustion turning the crank which turns the oil pump.

SonicVQ

I just checked the ignition coils from my 2011 G37 Sport Sedan and they say "HANSHIN, AIC-2809B, 22448 EY00A" The last part is the Nissan/Infiniti part number. I think Z1 sent you the real ones.

As for low oil pressure not causing a misfire, I think it can...
What if the oil pressure is low, and the hydraulic valve lifter is not properly filled with engine oil and an intake valve doesn't fully open? > Misfire
What if the VCT (variable cam timing) can't position the cam to the correct position and the an intake or exhaust valve isn't fully closed? > Misfire

Keep in mind, a misfire is determined on the angular acceleration of the crankshaft after a combustion event. The ECM measures the acceleration of the crankshaft for each combustion event. If the acceleration is below a defined limit, a misfire is declared. If a valve is not fully closed during combustion, the rate of crankshaft acceleration may be lower and the ECM may declare this as a misfire.

SonicVQ

Checking oil pressure is a great idea. Just incase you havn't seen this, here is a good video that shows the process and specs for a G37/370z:

jfridge92

Thanks for the info Sonic VQ! Thankfully my car is a '13 so it "should" have the updated gallery gaskets, but just to be safe I'm going to check the oil pressure to rule that out. I actually just got the exact same pressure test kit in Motorvate's video in the mail today, so I should be able to get some test results in the next day or two.

Do you know what thread sealant Infiniti/Nissan recommend to use on the oil pressure sensor? He mentions to use a thread sealant when reinstalling the sensor, but I'm not sure what is recommended. A lot of google searching had a ton of recommendations for teflon tape, but common sense in my mind says teflon tape in an engine is a potential time bomb that shouldn't even be considered. I didn't see any sealant recommended in the FSM for the G37, does anyone know about this? Or does that sensor even need a thread sealant? If I can do it right the first time and not have to pull the sensor back out if it leaks, that'd be great!

SonicVQ

There is nothing wrong with using 2-3 turns of teflon tape, as long as you don't wrap the first 1/8" or so of the tip.
-OR- use the thread sealer recommended in the FSM: (Permatex 56521 on GI-22)
https://www.permatex.com/products/th...hread-sealant/

Selym

The VQ37VHR does not have hydraulic lifters.

SonicVQ

You are correct! Thanks for the correction.