Misfire or CVT failure imminent?

[Ilya]

The P0302 came back along with a P0300. However, my wife did not report any jerking or misfires while applying throttle like before.

How likely is it that my valve cover gasket is going and that oil is impacting the spark function? Is that a hard job on this vehicle for a general DIY mechanic?

[VStar650CL]

It's possible but I dunno if I'd call it likely. Oil has a pretty good dielectric, when it affects a plug it's usually a long term thing where oil softens the rubber and eventually causes an arc-through to the metal wall. With the #2 coil being new, I'm doubtful about that. Since it keeps coming back on #2, I'd see if the bank2 STFT shows any evidence of a vacuum leak or other abnormality, and if not, look first at stuff that only affects bank2 like the throttle body or MAF.

[Ilya]

A few different STFT captures at a various speeds as well as at idle (at a stop sign).

[VStar650CL]

It's hard to say much without RPM's and engine temp on display, but that second panel is concerning with a spike on bank2 but no corresponding enrichment on bank1. To see if it's vacuum, the trick is to take STFT at a fully warm idle, then raise the RPM and watch where it steadies out. If either bank is substantially positive at idle but drops to near 0% above 2000 RPM, a small vacuum leak is indicated on that bank.

[VStar650CL]

PS - I'm not sure I trust your scanner, the LTFT is a historical average that moves very slowly relative to STFT, so it shouldn't be bouncing around like that. I don't know if your scanner is looking at the parameters correctly.

[Ilya]

I took a short drive and parked up and then recorded while idling, revving slightly and driving back home. Does this help at all? (apologies, no option to embed here directly)

https://streamable.com/jyprel

[VStar650CL]

Yep, that's more like it. Not a vacuum leak, although b2 is running a tad richer than b1. Too late tonight for me to study the vid in depth, I'll take a better look in the morning.

[VStar650CL]

The only thing I see that's abnormal is that your idle speed is high (should be 625+/-) and your MAF behavior is very non-linear. I can tell you from rude experience that VQ35DE's are completely intolerant of a dirty MAF, you can get all kinds of nutty behaviors. You're showing about 52 cfm @ 1K RPM, try cleaning the MAF and see if that changes appreciably. If not, do an IAVL (CVTz50 has the capability, I don't think Torque does) and see if that causes an appreciable change. You can check before/after at any handy engine speed above idle, I just picked 1K because there's already a referent at 988 RPM in your recordings. IAVL can alter the idle speed, so that's why you always do comparisons at a higher point. IAVL is quick and easy but there are a couple rules, engine temp > 160F, trans temp > 104F, Park position, all electrical loads off.

[AZhitman]

Loving this discussion!

I'm a huge fan of BG44K, gently sipped through a small-diameter hose attached to the brake vac booster hose, while someone holds idle at 3k.

One can through the intake, one can in the tank. It's been a great recipe for Nissan engines since we were playing with VH45s back in the late 90s.

[Ilya]

The only thing I see that's abnormal is that your idle speed is high (should be 625+/-) and your MAF behavior is very non-linear. I can tell you from rude experience that VQ35DE's are completely intolerant of a dirty MAF, you can get all kinds of nutty behaviors. You're showing about 52 cfm @ 1K RPM, try cleaning the MAF and see if that changes appreciably. If not, do an IAVL (CVTz50 has the capability, I don't think Torque does) and see if that causes an appreciable change. You can check before/after at any handy engine speed above idle, I just picked 1K because there's already a referent at 988 RPM in your recordings. IAVL can alter the idle speed, so that's why you always do comparisons at a higher point. IAVL is quick and easy but there are a couple rules, engine temp > 160F, transmission temp > 104F, Park position, all electrical loads off.

Man, NICOClub (and I) owe you a TON of gratitude for the amount of insight you bring here.

I will pick up some MAF cleaner in the next couple of days and give it a cleaning + do the IAVL via CVTz50...my experience with Nissan MAF's is not great, are they still as sensitive to cleaning as I remember from my 4th Generation Maxima days? Or just more or less spray it with the CRC MAF cleaner from 6-12 inches away and let it dry?

Loving this discussion!

I'm a huge fan of BG44K, gently sipped through a small-diameter hose attached to the brake vac booster hose, while someone holds idle at 3k.

One can through the intake, one can in the tank. It's been a great recipe for Nissan engines since we were playing with VH45s back in the late 90s.

I put Seafoam through the Intake on both the QX60 and M56x two weeks ago, but did buy some BG44K and put that in the tank on the M56x...need to put the other bottle in the tank on the QX60 but waiting for a fill up to do so.

[VStar650CL]

I will pick up some MAF cleaner in the next couple of days and give it a cleaning + do the IAVL via CVTz50...my experience with Nissan MAF's is not great, are they still as sensitive to cleaning as I remember from my 4th Generation Maxima days? Or just more or less spray it with the CRC MAF cleaner from 6-12 inches away and let it dry?

They're sensitive to crud, and to cleaners which leave a film. MAF, carb, or intake cleaner are all fine, Brakleen and most alcohol-based stuff isn't. Don't spray it from 6", get that little tube right in its face. If there's a scrap of lint or butterfly wing trapped in a passage, you want to make sure you force it out.

[Ilya]

Cleaned the MAF yesterday, man much easier on these new cars (both of mine) than the Maxima...unscrew and slide out, don't have to disassemble the whole intake system.

[Ilya]

So, did around 1,000 miles for a trip from Charlotte to Columbus for a wedding this weekend and car ran perfectly the whole trip! Looks like most likely just needed to clean the MAF and run some seafoam (and BG44) through it a couple of times! Not sure the spark plug or coil pack was ultimately the issue.

[VStar650CL]

[Ilya]

Noooooo! Moniiiiiccaaaa!

Our friend, P0302, is back. But without the judder.

Ugh. Next thoughts?

[VStar650CL]

Get some 0.025" music wire or an 0.024~0.026" safety pin and check the pin-fits on the #2 coil connector. You should get palpable drag when inserting the wire, if there's little or no resistance then the spring inside the pin is shot. If that checks okay, back probe the three coil wires with the engine running and compare the readings to a coil on the other bank (since we know bank1 isn't misbehaving).

[Ilya]

Got it - will source some of that wire. Something like this?

https://www.amazon.com/Music-Wire-025-D ... 1_3?sr=8-3

[VStar650CL]

Yep, perfect. Just about all Nissan connectors use 0.025" receptacles except for large power connectors. So you can use that for pin-fits almost everyplace on the car.

[Ilya]

Yep, perfect. Just about all Nissan connectors use 0.025" receptacles except for large power connectors. So you can use that for pin-fits almost everyplace on the car.

Awesome - so basically, what we're testing here is that the harness itself that connects to the coil pack isn't 'loosey goosey', yeah? And if it is...I imagine there is a place to buy a new one and either cut the bad one off and resolder (I can do that myself) or somehow dismantle it and replace the plug by sliding the wires out and into a new one?

[VStar650CL]

Awesome - so basically, what we're testing here is that the harness itself that connects to the coil pack isn't 'loosey goosey', yeah?

Correct.

And if it is...I imagine there is a place to buy a new one and either cut the bad one off and resolder (I can do that myself) or somehow dismantle it and replace the plug by sliding the wires out and into a new one?

Those connectors fail pretty frequently from heat, so there are tons of pigtails available on eBay, Amazon, and probably the local parts store. Soldering is pointless, though. Using solder-shrinks will give you an easier repair that's just as strong and waterproof to boot. I'm as good as there is with an iron, I can hand solder TSSOP's and TQFP's without batting an eye, but there are now two things I'll never go back to -- New Jersey and hand-soldering wires.

[Ilya]

Awesome - so basically, what we're testing here is that the harness itself that connects to the coil pack isn't 'loosey goosey', yeah?

Correct.

And if it is...I imagine there is a place to buy a new one and either cut the bad one off and resolder (I can do that myself) or somehow dismantle it and replace the plug by sliding the wires out and into a new one?

Those connectors fail pretty frequently from heat, so there are tons of pigtails available on eBay, Amazon, and probably the local parts store. Soldering is pointless, though. Using solder-shrinks will give you an easier repair that's just as strong and waterproof to boot. I'm as good as there is with an iron, I can hand solder TSSOP's and TQFP's without batting an eye, but there are now two things I'll never go back to -- New Jersey and hand-soldering wires.

Hah! Very well then! Hadn't heard of solder shrinks before but quick Google and I am sold!

[Ilya]

Been very busy lately (and about to leave the country for almost a month soon) but finally got around to doing the music wire test. I felt pretty tangible resistance getting it in all three holes (there is a joke in there somewhere lol) so I think the connector is good. I took a video that I can post, if you think it's worth uploading.

I did try to back probe with my multimeter but unfortunately I couldn't get a reading - is there a special way or tool to do that?

I did also unplug each of the #2, #4 and #6 coil packs while the car was idling and the idle noticeably changed which is good.

One thing I noticed when I first started the car and immediately went to move it forward 5ft to be partially in the garage and out of the sun is the idle was VERY rough (we normally remote start it and don't come out to it for a couple of minutes to either let heat or AC - plus the oil - get going). But after about 30 seconds, it smoothed out and was totally fine.

[VStar650CL]

Is there any smoke on the cold starts or warm restarts? That could mean a leaky injector seal which is burning off after the car's been running for a bit. Besides smoke, a good clue for that is if it's throwing the misfire code within a minute or so after startup, but not at any other time.

My usual back-probing tool is a small safety pin. You slide it between the wire and the rubber and you can usually feel it make contact with the back of the metal pin.

[Ilya]

Is there any smoke on the cold starts or warm restarts? That could mean a leaky injector seal which is burning off after the car's been running for a bit. Besides smoke, a good clue for that is if it's throwing the misfire code within a minute or so after startup, but not at any other time.

My usual back-probing tool is a small safety pin. You slide it between the wire and the rubber and you can usually feel it make contact with the back of the metal pin.

No smoke that I have noticed (I do sometimes watch the car start up when I'm remote starting it while approaching).

So you put the safety pin in there and then use the multimeter to touch the safety pin and get a reading? Man, so simple hah.

[VStar650CL]

So you put the safety pin in there and then use the multimeter to touch the safety pin and get a reading? Man, so simple hah.

Yep.