Cylinder 4 misfire?

[Spike00513]

16684 - Random/multiple cylinder misfire detected
P0300 - 001 -

16688 - Cylinder 4
P0304 - 001 - Misfire detected

Flashing CEL, but intermittent
I switched Cyl.4 coilpack to #5, it didn't follow.

Any ideas?
Relatively new NGK longlife spark plugs

[jayiszraw]

Try switching the injectors

[jpulll]

If you switched coil packs, spark plugs and injectors around and still get a misfire, it's either a compression problem (doubtful) or you have an electrical line or connector for the coil pack or injector fried up. Good luck.

[eljay]

I switched a coil. I'll try the injector and plug.

Is it OK to re-use a plug or should I get a cheap new one?
(Since they have built-in crush washers)

If electrical, wouldn't there be a relevant code though?
Ex: "Open circuit, no signal", etc.

Could a VCG have failed, causing oil pooling and misfires?

You should be OK to switch the plugs for testing. Just torque them properly.
Not to send you down the wrong path, but if you checked the above (coils, plugs, wiring), unless it's always on the same cylinder, it could be caused by vacuum leaks too. Happened to me on my Golf previously.

[WB650]

I've been getting this randomly since February, only on cold start and replacing my MAF b/c that was throwing codes fixed this issue too

[jpulll]

I think it's only one cylinder. If that is the case it can only be plug, injector, coil pack, or compression issue...or electrical issue for the corresponding coil pack or injector. If it's multiple then the possibility of a vacuum leak/MAF issues arise. But in spikes case, like I said above, I believe it is just "cyl 4".

I can't think of anything else that would cause only one cylinder to misfire.

Think back to basic lawnmower engines, since you only have one jug misfiring. If it was misfiring or not starting...where would you check?....

[WB650]

On mine it would throw Random and Cyl 4 misfire

[jpulll]

Ha, I feel like a jackass now. Been ranting on about single cyl misfire and I see the very first line says random/multiple misfire. Sorry!

[eljay]

Ha, I feel like a jackass now. Been ranting on about single cyl misfire and I see the very first line says random/multiple misfire. Sorry!

Actually, your points are still valid. Unless there are codes for other cylinders, OP should troubleshoot the single cylinder misfire first.
I believe if you let a single cylinder misfire carry on for a while, you will eventually get the P0300 code
Some more helpful troubleshooting info:
http://wiki.ross-tech.com/wiki/index...4/P0300/000768

[SJorge3442]

Spike, I'd grab a set of NGJ BR8ES plugs (Copper's) and pull your fuel injector rails and clean and replace the o-rings on the injectors if you havent done this recently. Thats where I personally would start, but then again, I change plugs every 5K miles.

[Spike00513]

Spike, I'd grab a set of NGJ BR8ES plugs (Copper's) and pull your fuel injector rails and clean and replace the o-rings on the injectors if you havent done this recently. Thats where I personally would start, but then again, I change plugs every 5K miles.

I hear copper =
pros: better performance
cons: frequent replacement

It's on OEM laser platinum PFR6U-11G (NGK).
w/ serviced injectors and viton O-rings, all not that long ago.

I will take forum advice, but I wonder if this has anything to do with returnless fueling (rail gets hot), it seems to only happen after hot sitting. Early 3.0 were return-style.
It goes away after a bit of driving.

Or fuel filter? Maybe I should've ordered from GAP, ECS, dealer, etc., rather than here..
Clicky

[SJorge3442]

I hear copper =
pros: better performance
cons: frequent replacement

It's on OEM laser platinum PFR6U-11G (NGK).
w/ serviced injectors and viton O-rings, all not that long ago.

I will take forum advice, but I wonder if this has anything to do with returnless fueling (rail gets hot), it seems to only happen after hot sitting. Early 3.0 were return-style.
It goes away after a bit of driving.

Or fuel filter? Maybe I should've ordered from GAP, ECS, dealer, etc., rather than here..
Clicky

I cant imagine a misfire being caused by a fuel filter, but I've seen stranger things. The fact that cylinder 4 is on the drivers side, in the middle, makes me feel that if it were a fueling issue, it would have to effect one or both of the other cylinders too. I doubt this also has to deal with the fuel rail getting hot.

I buy my fuel filters from Europa, just because they have fast shipping to me, and I always use maan filters. I change that every year, regardless of mileage. I also run the copper plugs, because I like pulling them so I can see whats going on in the engine at a regular interval. Although neither my oil or plugs have been changed since January, since I only drove my car a whopping 1400K miles so far this year, I plan to change the oil and plugs Thursday night before I drive from Philly to Pittsburgh and back this weekend (~700 miles). I can't comment on the performance of copper plugs with any hard science, but I too have heard copper have better performance, but only last for ~5K miles.

[SJorge3442]

Also, I lied about the spark plugs. Those are the part number for my jetski...whoops. The plugs for the 3.0 are BKR6E

[ECS Tuning-Audi]

I was chasing misfire codes for a while now, but pretty sure I have it all sorted out now. For what its worth you may want to do a boost leak test. If you have a leak and the engine isn't pulling enough vacuum at idle it will cause misfires. I had a blown PCV and a cracked crank case breather tube which was causing the majority of the issues.

Areas worth checking are the PCV line that leads to the manifold (near the throttle body on the underside) the injection pump (looks like a big check valve towards the fire wall) and your crank case breather tube/PCV. If there is a big enough leak it can definitely cause misfires.

Do you have a boot gauge installed? If so you could easily see if you're pulling enough vacuum.

Jason

[Spike00513]

I was chasing misfire codes for a while now, but pretty sure I have it all sorted out now. For what its worth you may want to do a boost leak test. If you have a leak and the engine isn't pulling enough vacuum at idle it will cause misfires. I had a blown PCV and a cracked crank case breather tube which was causing the majority of the issues.

Areas worth checking are the PCV line that leads to the manifold (near the throttle body on the underside) the injection pump (looks like a big check valve towards the fire wall) and your crank case breather tube/PCV. If there is a big enough leak it can definitely cause misfires.

Do you have a boot gauge installed? If so you could easily see if you're pulling enough vacuum.

Jason

N/A 3L V6. Seemed like it only started a few weeks ago at most. More prevalent at low RPM and under load.
Vacuum lines were replaced with OEM ~40k mi ago, new plastic tees. And PCV pancake.
Original plastic tubes though, maybe it's time for the heater hose fix..
Maybe I can check for PCV health by putting a glove over the oil cap port, to see if it vacuums or inflates?

[ECS Tuning-Audi]

N/A 3L V6. Seemed like it only started a few weeks ago at most. More prevalent at low RPM and under load.
Vacuum lines were replaced with OEM ~40k mi ago, new plastic tees. And PCV pancake.
Original plastic tubes though, maybe it's time for the heater hose fix..
Maybe I can check for PCV health by putting a glove over the oil cap port, to see if it vacuums or inflates?

Oh dang lol. Still can apply the vacuum tips. A quick vacuum test is if at idle the oil cap is difficult to remove and it chokes out there's something funky going on vacuum wise. If you can remove it easily and while loose it just hops around a bit you should be OK.

Jason

[WB650]

I'm 1.8 but yeah the MAF didn't fix this, started my car this morning and got the flashing CEL which shows Cyl 4. Seeming like its a vac leak indeed. This is gonna be a pain

[Spike00513]

New to the mix,
random no hot start. Will check for DTC(s)

I popped the hood and re-plugged the CPS, it worked. Maybe it would've too, by re-connecting the battery.

I heard somewhere this is all due to a faulty relay not allowing the ECU to get power at times.
Considering the CPS is good, what else could it be.
Hence why it cranked but didn't run.

Cranking only requires a starter and battery.
Running requires an ECU.

I didn't check the spark plug yet but I'm sure it's fine, same for injectors, they're freshly serviced (flow-tested, cleaned, etc.).



-------OR-----
Could it be lack of RFI/EFI shielding on the CPS->ECU harness? The wire wore out and broke so I put a crimp, the shielding contact no longer established.
But that was like a year ago. And these symptoms seem random.
If it was a shield issue, maybe it would happen consistently.

Not sure if the shield works as a ground.
Maybe I can wrap some aftermarket, or tear apart the harness to put a whole new wire..

The shielding is to block interference "to" the CPS not "from" it, if the CPS receives any electrical interference it could cause it to not relay the proper information to the PCM. My advice? redo the job with the shielding in place.

[Spike00513]

Pulled the ignition.
Spark plugs and coilpacks look fine.

I guess next up is,
switching fuel injector

and cleaning interior relays.
Could this be water in the ECU?

--------side-note,
intermittent door connectivity issues (mirror won't tilt, etc.), could that be related?
Maybe some ECU issue causing all this?

[Spike00513]

Pulled the ignition.
Spark plugs and coilpacks look fine.

I guess next up is,
switching fuel injector

and cleaning interior relays.
Could this be water in the ECU?

--------side-note,
intermittent door connectivity issues (mirror won't tilt, etc.), could that be related?
Maybe some ECU issue causing all this?

[old guy]

Water in the relays would not cause a misfire specific to one cylinder. I think you are on the right track by switching the #4 injector with a different one and see if the misfire follows.

[Spike00513]

Water in the relays would not cause a misfire specific to one cylinder. I think you are on the right track by switching the #4 injector with a different one and see if the misfire follows.

Or rain in the ECU?
fuel filter issue?
Rad. fan isn't turning on, causing unoptimal hot conditions?
Bad gas?

[old guy]

Maybe I misread the original post but isn't your misfire primarily on cylinder #4?

[diagnosticator]

I hear copper =
pros: better performance
cons: frequent replacement

It's on OEM laser platinum PFR6U-11G (NGK).
w/ serviced injectors and viton O-rings, all not that long ago.

I will take forum advice, but I wonder if this has anything to do with returnless fueling (rail gets hot), it seems to only happen after hot sitting. Early 3.0 were return-style.
It goes away after a bit of driving.

Or fuel filter? Maybe I should've ordered from GAP, ECS, dealer, etc., rather than here..
Clicky

There is no merit to the copper electrodes/plugs improving performance myth.

[diagnosticator]

Pulled the ignition.
Spark plugs and coilpacks look fine.

I guess next up is,
switching fuel injector

and cleaning interior relays.
Could this be water in the ECU?

--------side-note,
intermittent door connectivity issues (mirror won't tilt, etc.), could that be related?
Maybe some ECU issue causing all this?

Replace #4 coilpack with a new coilpack. If the #4 misfires do not stop with a new coilpack, then there is a likely electrical fault in the #4 power supply or ground circuit.

[WB650]

How old is your fuel filter, I believe mine was last changed at 70k, so 70k miles ago. I think I may have this done. Couldn't hurt. Will have to go over paper work and make sure I've havent had it done already and can't remember

[SJorge3442]

How old is your fuel filter, I believe mine was last changed at 70k, so 70k miles ago. I think I may have this done. Couldn't hurt. Will have to go over paper work and make sure I've havent had it done already and can't remember

Cylinder 4 IS the furthest cylinder from the fuel pump so this could be it. I change these EVERY year on every vehicle, but I know plenty of people over look this item.

[WB650]

Cylinder 4 IS the furthest cylinder from the fuel pump so this could be it. I change these EVERY year on every vehicle, but I know plenty of people over look this item.

Yeah, you guys are 3.0, I'm 1.8, not sure if the same but I think I'll def have this done. I'll start my car and it feels a little rough, sometimes no light will come on, other times as soon as the SAI turns off I get either a flashing CEL then it stays solid or turns off, or it doesn't flash and it stays on. Always Cyl 4.

[AutoMax]

I had a similar issue with cylinder 3. Turned out to be a coil harness issue.



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[WB650]

Check my records and I had a shop replace my filter at 120k so that was 27k ago

[diagnosticator]

Pulled the ignition.
Spark plugs and coilpacks look fine.

I guess next up is,
switching fuel injector

and cleaning interior relays.
Could this be water in the ECU?

--------side-note,
intermittent door connectivity issues (mirror won't tilt, etc.), could that be related?
Maybe some ECU issue causing all this?

No, not related to any ECU issues. Check the wiring harness in the boot at the driver's door jamb. It is known that the wires break in the boot after a long time with many door open/close cycles.

[diagnosticator]

New to the mix,
random no hot start. Will check for DTC(s)

I popped the hood and re-plugged the CPS, it worked. Maybe it would've too, by re-connecting the battery.

I heard somewhere this is all due to a faulty relay not allowing the ECU to get power at times.
Considering the CPS is good, what else could it be.
Hence why it cranked but didn't run.

Cranking only requires a starter and battery.
Running requires an ECU.

I didn't check the spark plug yet but I'm sure it's fine, same for injectors, they're freshly serviced (flow-tested, cleaned, etc.).



-------OR-----
Could it be lack of RFI/EFI shielding on the CPS->ECU harness? The wire wore out and broke so I put a crimp, the shielding contact no longer established.
But that was like a year ago. And these symptoms seem random.
If it was a shield issue, maybe it would happen consistently.

Not sure if the shield works as a ground.
Maybe I can wrap some aftermarket, or tear apart the harness to put a whole new wire..

The CPS is not sensitive to outside electromagnetic interference, (in generates a sine wave signal, ) but the ECU is sensitive to EMI on some inputs. If EMI gets into the CPS signal return wire to the ECU, the clean sine wave signal generated by the CPS, can be distorted and the EMI noise in the CPS signal to the ECU resulting in an unreliable sensed engine speed signal in the ECU. Besides crankshaft speed, the CPS provides a single once per rotation blip that is combined with the signals from the cam position sensors, allows the ECU to determine what operating stroke each cylinder is on for fuel injection and coilpack spark timing functions. Any field wiring connected to a sensitive input at the ECU must be shielded against EMI. A broken or disconnected shield won't cause only one cylinder to misfire. New shielded wires can be run outside the main harness if there is something wrong with the shield in the original wiring. EMI shielding intercepts and grounds EMI preventing transmission in the wiring.

[dmanisgnarly]

I've seen the fuel injector harness chafe from excessive vibrations using a stiff snub mount..did you trace the whole spark & fuel harness? They tend to get brittle over the years.. my headlights caught on fire from the wire coating dry rotting and falling off.