Thread 28689204

I have this weird random cylinder misfire, triggering error P0300. It misfires on idle and when I put one gear and give it some throttle at low revs, the car chokes, but when I go past 3000rpm however, it is not noticeable.
I took out the spark plugs and they were burnt at the tip, and I found some oil on the threads and in one of the coils. I used some brake cleaner and a wire brush and scrubbed all the carbon buildup on the spark plugs until they looked clean, but it didn't help.
I do notice that when I really put some heat on the engine by revving close to the limiter, it will become normal even on idle, without misfiring. If I leave it idling it will be normal for a couple of minutes and then start having one misfire every 10 seconds, and then only after like 5 minutes it will start misfiring every cycle again.

The spark plugs are shitty Bosch Super 4s, and the coils are Bosch for cylinder 2 and still on original ones on the rest. I bought the car used and it came like this otherwise I'd have swapped all coils and put some NGKs.

New spark plugs arrive between tomorrow and monday, I don't know if it will fix it, but I needed new ones anyway.

Can anyone give me some insight on other possible causes if spark plugs won't fix it?

>>28689204 (OP)
Is the ignition coil OK?

>>28689204 (OP)
are all your spark plugs that filthy?

>>28689204 (OP)
Seee what normal OEM plugs do.
Those multi strap plugs are often shit.

>>28689204 (OP)
Raped by Porsche

>>28689219
I didn't test them with the engine running (will try if new plugs don't fix it). But I searched and found a video which showed that when they go bad they have this bulge thing on the side, and none of the coils had it.
I also checked every vacuum line for leaks, and didn't find any.
What pisses me is that scanning codes only gives me random misfire and not one specific cylinder so I can't tell what exactly is wrong.

>other possible causes if spark plugs won't fix it?
coils, fuel pump, battery, clogged rail, alternator, ecu mapping, etc. just put in the new plugs and see if the misfires are still there. note if it's only certain cylinders to help with troubleshooting

>>28689235
Yeah, they were mostly all like this, just one or two slightly better but still with some gunk. Took me a whole can of brake cleaner and a wire brush to make them decent again.
>>28689241
I have no clue who got the old owner to put this garbage on it, I don't know anyone who has ever liked these shit 4 pole spark plugs. The spark position isn't even vertical. I bet he thought it would have 4 sparks and thus, better ignition.

>>28689249
coils can be bad even without any visual indication
>scanning codes only gives me random misfire and not one specific cylinder
how are you pulling codes? a cheapo OBD2 bluetooth scanner and the Torque app should give you specific cylinder misfire counts

>>28689255
Clearly 4 is greater than 1.
& therefore better.

>>28689253
Those should give more than just random cylinder misfire error code, shouldn't they?
>>28689259
I'm using a cheap bluetooth ELM327 scanner and the Car Scanner app. Is Torque better? I'm thinking of buying one of these apps just for my Nissan since the cable I use with the laptop only works with BMWs, which app do you reckon would be the best?

>>28689255
>Yeah, they were mostly all like this, just one or two slightly better but still with some gunk. Took me a whole can of brake cleaner and a wire brush to make them decent again.
What does your PCV system look like?

>>28689274
>I'm using a cheap bluetooth ELM327 scanner and the Car Scanner app. Is Torque better? I'm thinking of buying one of these apps just for my Nissan since the cable I use with the laptop only works with BMWs, which app do you reckon would be the best?
Buy a TOPDON J2534 adapter and use the OEM programs so you have full bidirectional control. if thats too expensive then some chinkshit J2534. The adapter should work with any car, and then you can just find pirated versions of whatever the OEM software is. For Nissan it is CONSULT III

>buy a TOPDON J2534 adapter
utterly retarded consooomer advice. there's no need to spend anywhere near this much
>>28689274
my $20 BAFX reader + Torque pro hasn't let me down in 10 years

>>28689278
I didn't get to remove the valve, just the tube since I needed to remove it anyways for easier access, but the tube was oily so I don't think it is stuck. I'll remove it and check it tomorrow and now that I think of it, I have a catch can I never got to use in my daily, so guess I'll use this opportunity to install it here.

>>28689249
These ignition coils are failing terribly. My Delphi lasted 30k km, and I replaced the spark plugs every 10k km. I got 50k km on the Hitachi, and the engine started running rough again.

I suspect that producers deliberately making shoddy parts (they break easily, so you have to buy new coils and new spark plugs).

>>28689327
I think it's the Bosch one if that's the case. I forgot to mention that when I pulled the car over to remove the coils, the Bosch one was almost room temp, while the other ones were a bit warmer.

Bro out here not replacing all plugs as a set, mix matching other parts and doing all types of
>FUCK NO!
stuff and wondering if the problem is an easy diagnose.
Is this entire thread a joke?

I'm half curious if you got a cam lobe wiped or failed lifter or something along those lines, which is the ugly side of what causes misfires.

>>28689287
>i dont know what bidirectional control is
you really are this retarded arent you

>>28689249
In the past on my VQ30DET the coils once sufficiently aged and degrading would have a weak spark after heating up. You can check the primary / secondary winding and see if it's in spec cold, then get them to operating temp where you are having misfires and check them again.

If they have replaced one, either due to age, oil fouling, or carbon tracking....you probably have other failing or on the way out coil/ plug combos.

Don't mix and match : oil foiled or carbon tracked plug boots and insulators on the plugs can cause intermittent issues and can even kill the coils long term.

I'd also fall in line with what other people say, ditch the multi strap bullshit plug, and go with the platinum laser NGK the vq motors call for.

Another thing to note is that the two coil styles have different conductor springs inside the boot. So if someone just swapped a coil and kept the factory plug boot it may not actually be making physical contact with the coil and it's arcing the gap, leading to a weekend spark.

>>28689727
how does bidirectional control help with OP's misfire issue?

>>28689327
Half the time its just because youre just using the wrong plugs for your car. I'm assuming your poor and own a Japanese car so buy some Denso plugs and throw them in

>>28689775
OP here.
I replaced all plugs and started the car. Started instantly and without any misfires for about 10 minutes on idle. Then it started having one or two every 30 seconds. After it got to operating temp it started again, and wouldn't go even after shutting the car down, waiting for it to cool and start it again.
Scanning the error codes now identifies a misfire on cylinder 6 only. I swapped out the coils from cylinders 6 and 4 and I got the random/multiple misfire code. Changed the coils back and I got the cylinder 6 misfire code again. Seems the coil on cylinder 6 is bad.
I'm just going to order a whole new set of coils, might just keep the Bosch one as spare, any brand suggestions? The car isn't boosted, so I don't see any need for upgraded ones yet. NGKs, Bosch, Denso, or really any one should do the job?
Also, pic rel, the tube seals are getting pretty bad, so I'm going to order new valve covers, I might as well get them in aluminium. Since I'm pulling out the entire plenum to get access, I'll probably replace all the plenum gaskets while I'm at it. Anything else you guys recommend doing since while the valve covers are out?

Didn't these things have major plenum issues? There's an aftermarket spacer. Since you seem to be exhausting most avenues.

>>28692016
Clean the throttle body if you can

>>28692121
They did, the stock plenum starves the front two cylinders. But I do have a spacer for it, only downside is it's a plastic one. No leaks so far but it's also one of the things I'm going to upgrade.
>>28692123
Yeah that's a good idea. Especially since I installed a catch can today, might just clean the throttle body and plenum to do the whole job.

>>28692016
For coils I always like oem or NGK.
I think mitsubishi, Hitachi, and hashin are all oe for the VQ coils depending on the years.

Had good luck with the NGK and the oe Hitachi ones. I'm factory boosted but it's nothing crazy.

>>28692239
I put a catch can on mine and was pretty shocked to find that under normal driving it stays bone dry. It really only has any oil accumulation if you are at full boost and high rev for extended periods. It's temporary for me so it looks like ass.

I'm not very famillure with the 3.5 litre motors, but other things to consider while the plenum is off is cleaning out any ancillary control valve bodies, smaller vacuum lines, possibly replacing the breather balance pipe and the PCV between the valve covers etc

>>28692412
I’m thinking of going with NGK but DIYing an adapter to put the GTR coils instead.
I’m curious about your catch can. Mine came with a breather, but with the option to remove the air filter and pipe and close it with a bolt. I ended up taking this filter out along with the pipe and plug the hole with the bolt to make it just like yours. Do you reckon the breather would help or actually make it worse by causing a vacuum leak?

>>28693080
Mechanically I do not understand the point of the cheap breather catch cans like this. If you pipe it back into the factory PCV system, you have now introduced a massive vaccum leak, and at the same time negated any real advantages of having the PCV in the first place.

Now you could use another one way valve to the breather which should prevent the system from pulling in through that filter, and only release extra pressure in the rare event that is happening. But on a relatively Low Rev, NA, Low power motor I do not see this really being beneficial.

TLDR is Either run the catch can closed if you want a functional PCV and partial crank case vacuum for efficiency, and oil seepage control. Or just cap the PCV feed line on the intake plenum, and slap that filter on top of the PCV in your valve-cover and let it vent straight to atmosphere.

>>28693216
Yeah I figured as such. I had it installed with the breather first but gave it a second though and removed it and plugged it. Glad I did I guess. I’m still going to buy a second one for the driver’s side. Throttle doesn’t look too dirty, but any less oil that goes in that’s good for me. Did you have a dual can setup in your engine?
Guess I’ll buy a compression tester too from Amazon and run some tests while the damn coils don’t arrive. Fucking parts shops here have zero shit in stock other than oils and filters.

>>28695297
I do not have a dual feed currently. I still rely on the balance tube that runs between the valve covers under the intake plenum, and the single PCV on the drivers side cover.

No matter what I do, I am going to eventually plug the bung on the drivers valve cover, and run a PCV from each covers balance nipple, then T it into the vacuum at the manifold. This will also clean up the vacuum hose routing by letting me more or less curl the drivers side line to the passenger side fuel rail, and vise versa hugging it in closer, and eliminating the need for the complex formed rigid PCV hose from the factory.

>>28689204 (OP)
i had an injector that was leaking that would give poor performance and a misfire at idle and start hard. but at higher rpms it would work well. my plugs were dirty and wet as well.

>>28695426
I did not discard that option, I have often mixed strong octane boosters with the fuel, and slightly abused on the dosage.
But I did not get too lean/too rich error codes, did yours put out these codes?

>>28689204 (OP)
This could be anything from a bad battery, poor servicing, bad ground, chewed wires, fried ecu, bad coil, bad tune, bad injectors, out of spec valves

Do all of your basic maintenance tasks and get your car at a good baseline

Fresh oil, fresh fuel, fresh gaskets, fresh filters, fresh plugs

Then start swapping coils around to see if misfire continues

Now start replacing parts with quality items starting with serviceable consumables first

>>28695849
>Fresh oil
Check. Used engine flush on old oil and put new oil along with ceramic lining additive.
>Fresh fuel
I’m always on fresh fuel as I put a lot of miles on it, it doesn’t last more than 3 weeks between full refills.
>Fresh gaskets
This is where I haven’t gotten to yet. But new aluminium valve covers kit is already on the way with fresh gaskets. Will order a plenum gasket even though the one it has doesn’t look very old, plus I checked there for leaks and it didn’t have any.
>Fresh filters
Also done all of them, except the fuel one, couldn’t find one available when I did maintenance on it.
>Fresh plugs
Done, already installed them, which changed error codes from random misfire to cylinder 6 misfire.

But you mentioned about the bad ground and I did have a corroded ground battery cable that caused the car to shut off completely about 5 months ago. I ended up replacing it with a larger better quality one and replaced both terminals as well. Battery was also replaced.
Is there any other ground cables I should replace just for safekeeping? Couldn’t find any good diagrams that show me exactly where are the ground cables.
Also I can hear a faint rattle when driving, could this be a cracked catalytic converter and could that cause the misfire?