Misfire or CVT failure imminent?

[VStar650CL]

Should we disband this troubleshooting until it comes back?

I'd say yes. Those readings are perfectly healthy, and the 20mV difference between block and battery means your harness grounds are healthy as well. Electrically, we're running out of candidates.

[Ilya]

Should we disband this troubleshooting until it comes back?

I'd say yes. Those readings are perfectly healthy, and the 20mV difference between block and battery means your harness grounds are healthy as well. Electrically, we're running out of candidates.

Good deal! Will keep an eye on it while in FL and report back, although won't be able to troubleshoot much until I get back to NC in mid-October. Good thing I got my inspection done, I have 12 months to figure this out IF it comes back .

Thank you for all the help, as always VStar!

[Ilya]

Small update - in FL for a few weeks and had a 'roughish' idle at start one morning followed by CEL on about 35-40 seconds later. Also had a few very faint 'jerks' while accelerating onto the interstate but fine after that. Most people probably wouldn't have noticed it but I'm always looking for it.

[VStar650CL]

It's beginning to seem like this thing only misfires cold, and when that isn't a bad coil (which I think we've pretty much eliminated), it usually means a cranky injector.

[Ilya]

It's beginning to seem like this thing only misfires cold, and when that isn't a bad coil (which I think we've pretty much eliminated), it usually means a cranky injector.

Definitely seems to happen cold more often, but would the jerking stay even after it gets hot if the initial start up THAT time was less than great? Is something 'thrown off' during the process?

[VStar650CL]

If it's the injector, it probably has an intermittent case of mechanical stiction. So yes, it's entirely possible it could continue to hiccup whenever it feels sticky. That can be hellishly difficult to diagnose, because there's no way to look at the A/F from an individual cylinder. All you can really do is replace the injector and cross your fingers.

[Ilya]

If it's the injector, it probably has an intermittent case of mechanical stiction. So yes, it's entirely possible it could continue to hiccup whenever it feels sticky. That can be hellishly difficult to diagnose, because there's no way to look at the A/F from an individual cylinder. All you can really do is replace the injector and cross your fingers.

Is this a complex/expensive job?

[VStar650CL]

Complex enough, the plenum has to come off and the fuel rail needs to be removed. I'd call it "exacting", not rocket science but not simple either.

[Ilya]

Complex enough, the plenum has to come off and the fuel rail needs to be removed. I'd call it "exacting", not rocket science but not simple either.

Looks to be $200/ea, give or take. Not terrible expensive. Will have to do some research.

[Ilya]

Could this little bit of coolant be what is ultimately causing my issues (it still does infrequently happen). Do I need a gasket job or something? Or do we think it's still a sticky injector?

[VStar650CL]

Could this little bit of coolant be what is ultimately causing my issues (it still does infrequently happen). Do I need a gasket job or something? Or do we think it's still a sticky injector?

That's a smoking gun, especially considering it exhibits the miss when cold. You have a teeny-tiny head gasket leak. What happens there is that the cooling system builds pressure after the engine shuts down because the coolant is cooking against the hot block with no flow, but there's no longer any countervailing compression from the cylinder to push back the other way. So coolant dribbles out into the cylinder and may foul the plug, but the foul clears after the coolant gets pushed out.

[Ilya]

Ugh...aren't head gasket jobs usually very messy and long? It's one thing to pull the intake and change an injector, but how much more work is the head gasket?

[VStar650CL]

Basically the cats plus the whole front of the engine need to come off before you can unbolt the heads. Very big job. Eventually it will get worse, but for a leak that tiny, you might get by for quite awhile with something like Blue Devil sealer.

[Ilya]

Did a quick google on that Blue Devil sealer and I think I'm going to go that route. I plan to get rid of this vehicle in 2-3 years (40-50kmi) anyway to get the wifey something newer.

[Ilya]

This issue is still plaguing this car but it's very weird - it'll be fine for 4-5 weeks and then one day it'll just have sputter after sputter and then be fine again. I'm going on another trip from NC <> FL so decided to replace the #2 spark plug again for good measure and here is what the one that was in there (after only being there for 23kmi - installed at 123kmi and removed at 146kmi) looks like. I haven't done the Blue Devil or anything like that, yet...

[VStar650CL]

That's actually a really nice burn. Teeny bit of ash deposition (that's probably from additives) but nothing worrisome. I'm starting to wonder if maybe you have a bank2 cam sensor that's getting invisible hiccups. Halls can get some very funky "phase" errors that can shift a whole bank by up to 30 degrees, but because the cam has an asymmetric reluctor, you can also get phase shifts which only affect certain cylinders. I've only ever personally seen that once, but we're running out of possibilities here.

[Ilya]

Hmm, okay, good to know. I thought for sure you were going to tell me that spark plug is toast after 23kmi but glad to hear otherwise hah.

Seems like the cam sensor is pretty easily accessed just be removing the intake snorkel on the driver side of the engine bay on that front bank, is that correct?

Seems like the part number is 23731-JA11B which isn't terribly expensive. I don't mind throwing a few bucks at this problem if it saves me from having to replace the vehicle earlier than I want (2-3 years). Do I need two of these, one for the intake and one for the exhaust?

[VStar650CL]

Yep, it's the same p/n for both intakes and both exhausts. Bank1 doesn't seem to have any issues, so I'd just replace both bank2 sensors. Super easy on the front bank.

[Ilya]

Good deal!

This car is starting to show it's age. On my long trip today, going slowly full right turn I heard and felt a grinding on the front left tire (I believe). I'm guessing hub assembly is shot.

The joys of 150kmi vehicles...

[Ilya]

Got the new camshaft sensors from Amayama, installed them.

The car has been noticeably misfiring now for like 3 days steady. Before it would randomly happen and might not happen for weeks at a time. Now it's pretty much constant.

Before starting the car, I cleared the codes. Immediately upon starting, I could still feel it misfiring. Immediately upon starting a pending P0302 returned.

I'm worried about using the Head Gasket Sealer as I've read that it can block heater cores, etc. What is the level of risk with it, really? Is my worry misplaced?

[VStar650CL]

The stuff with pellets like Bars Leaks is pretty dangerous. Because Nissans have open-flow heater cores with no water valve, the powder and crystallizing types aren't very risky. One of my customers had good luck with Blue Devil, he added it a couple years back for a very tiny head gasket leak on an Xterra and the car was still running fine as of the last time I saw him, maybe a month ago.

[Ilya]

Okay, that makes sense.

Should I leave the car parked for now? Any risk of grenading this thing until I get some Blue Devil? Do I need to do anything after putting it in like change the plug again?

[VStar650CL]

I think I'd park it since your miss has become frequent. That plug you pulled looked fine except for being a bit ashy, so I wouldn't bother with that. Drain a little from the system if necessary to get the whole bottle in, don't put it in the reservoir. Give the car a long drive to make sure it's thoroughly mixed, then park it till the engine cools completely. Blue Devil is a crystallizing type, so you need heat and static pressure first so it penetrates the breach, then a total cool-down for it to plug it.

[Ilya]

I bought the Head Gasket Sealer bottle (32oz) on Amazon but I guess I got the one that requires a bit more work and removing the Thermostat, etc. Evidently there is a smaller bottle known as 'Pour-n-Go' that doesn't require removal of the thermostat. I should have it by Wednesday.

The one I got: https://www.amazon.com/dp/B000NOO798

The one I was supposed to get? https://www.amazon.com/BlueDevil-Pour-N ... rue&sr=8-1

AI made the suggestion to remove the spark plug and unplug the coil pack on the cylinder I'm having trouble with during the 50-60 minute drive/idle. Stopping the combustion pressure in that cylinder will help the sealer find the leak and bond to it? Is that just AI being dumb or is that something I should do?

Why you should pull the #2 plug during the 50-minute idle:
Since you have a steady misfire, there is likely a constant "breach" at the gasket.

If the plug is in and firing, the combustion pressure (hundreds of PSI) will blow the sealer away from the crack before it can harden.

If you remove the #2 spark plug and disconnect its coil, the piston will move up and down without "firing." This creates a vacuum that pulls the BlueDevil into the crack, allowing it to bond properly.

It also says:

Confirm Coolant Level: Make sure your radiator is full of water (not 50/50 coolant) when you start the process, as the sealer works best with water as the carrier.

Do I need to drain the coolant completely and fill it with distilled water? And then flush it again to fill with 50/50 coolant after a little while of driving with this? My coolant was changed at 105kmi (6/10/2024) so it's nearing time to replace anyway (another 5-6kmi or so).

Side quest(ion): Last time I was trying to get to the plug, I couldn't remove one of the bolts holding the engine cover on all of a sudden (left, passenger side). Removed it dozens of times. Is there a trick to get it out (it just spins right now) without basically cutting the engine cover up to get to it with pliers later? Ugh, this damn car all of a sudden.

[VStar650CL]

The trick with getting sealers to work is to build up pressure in the system, then let it cool off. The AI is right that the sealer can't work while the engine is running, but for a very small leak you don't need to get fancy like you would with a large one. After you shut the engine off the coolant stops flowing and whatever is in the block cooks against the hot metal, causing maximum heat (and pressure) about 5 minutes after shutdown. That will force the sealer into the breach. With a large leak that doesn't work so well, because you're generally losing coolant and the air in the system stymies pressure buildup. But then again, with a large leak sealer is usually hopeless.

I usually use a hook tool to get underneath the head of a spun screw, to exert some upward pressure while spinning it to help what's left of the threads bite.

[Ilya]

The trick with getting sealers to work is to build up pressure in the system, then let it cool off. The AI is right that the sealer can't work while the engine is running, but for a very small leak you don't need to get fancy like you would with a large one. After you shut the engine off the coolant stops flowing and whatever is in the block cooks against the hot metal, causing maximum heat (and pressure) about 5 minutes after shutdown. That will force the sealer into the breach. With a large leak that doesn't work so well, because you're generally losing coolant and the air in the system stymies pressure buildup. But then again, with a large leak sealer is usually hopeless.

I usually use a hook tool to get underneath the head of a spun screw, to exert some upward pressure while spinning it to help what's left of the threads bite.

Got it. Don't get fancy with pulling the plug, etc. and no need to do this with just water in the system - change my coolant in 5-6kmi as planned.

I was thinking of just trying to get a pry bar under the cover just enough to hold the bolt mount just enough so glad to read you approach it similarly.

[VStar650CL]

That will work too if you have enough room for a bar. Anything that puts upward pressure on the screw head should do the trick.

[Ilya]

Alright. So, today was Blue Devil day.

I changed the oil and filter, air filter, cabin filter and rotated the tires and then got on with the tedious job of coolant DIY. I decided not to just pour in the sealer and instead did 2x coolant drain and fills using distilled water instead. By the 2nd drain and fill, the water was still blue but getting lighter.

I put the Blue Devil in, added some more distilled water and went for a 60 minute drive averaging around 55-60mph. I monitored the temps on the dash as well as using the Torque app and they hovered between 186F and 203F, so all looked good. The car has been parked now since I got home.

It did stutter a couple of times during the drive (particularly at the very end as I was at a stop sign), but considering it was idling rough consistently for a week before the Blue Devil, I'd say it definitely improved. Lets see how it runs after it's had time to work.

I plan to do a last drain sometime mid-week if schedule allows and then fill it with Zerex Asian Vehicle Blue 50/50 coolant and add a bottle of Water Wetter for good measure.

[Ilya]

Checked oil dipstick this morning and oil looks good, no milk. Topped up distilled water for now and ran the car for a bit and then went for a short drive (5 min). Idle has a bit of a stutter but driving seems okay. Did have a pending P0302 code that I cleared.

Taking the car to Easter service so we'll see how she does the rest of the day.

[VStar650CL]

Happy Easter all!

On a VQ you pretty much need to have a complete blowout in order to get a milkshake. The sleeves are siamese and the cooling jacket (blue) completely surrounds them, so for coolant to reach both the cylinder and the oil passages (red) requires the head gasket to blow in opposite directions. The most common blowout involving a single cylinder is cylinder-to-cooling-jacket midway between the head bolts (green), which is probably what you have. Because of the siamese sleeves (common on many Nissan designs) it also isn't uncommon to get blowouts between cylinders without it ever reaching the coolant. When you get a misfire in adjacent cylinders with no coolant loss, that's often the guilty party.